/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * KVM/MIPS: Instruction/Exception emulation
 *
 * Copyright (C) 2012  MIPS Technologies, Inc.  All rights reserved.
 * Authors: Sanjay Lal <sanjayl@kymasys.com>
 */

#include <linux/errno.h>
#include <linux/err.h>
#include <linux/ktime.h>
#include <linux/kvm_host.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/fs.h>
#include <linux/bootmem.h>
#include <linux/random.h>
#include <asm/page.h>
#include <asm/cacheflush.h>
#include <asm/cacheops.h>
#include <asm/cpu-info.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
#include <asm/inst.h>

#undef CONFIG_MIPS_MT
#include <asm/r4kcache.h>
#define CONFIG_MIPS_MT

#include "interrupt.h"
#include "commpage.h"

#include "trace.h"

/*
 * Compute the return address and do emulate branch simulation, if required.
 * This function should be called only in branch delay slot active.
 */
unsigned long kvm_compute_return_epc(struct kvm_vcpu *vcpu,
        unsigned long instpc)
{
        unsigned int dspcontrol;
        union mips_instruction insn;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        long epc = instpc;
        long nextpc = KVM_INVALID_INST;

        if (epc & 3)
                goto unaligned;

        /* Read the instruction */
        insn.word = kvm_get_inst((u32 *) epc, vcpu);

        if (insn.word == KVM_INVALID_INST)
                return KVM_INVALID_INST;

        switch (insn.i_format.opcode) {
                /* jr and jalr are in r_format format. */
        case spec_op:
                switch (insn.r_format.func) {
                case jalr_op:
                        arch->gprs[insn.r_format.rd] = epc + 8;
                        /* Fall through */
                case jr_op:
                        nextpc = arch->gprs[insn.r_format.rs];
                        break;
                }
                break;

                /*
                 * This group contains:
                 * bltz_op, bgez_op, bltzl_op, bgezl_op,
                 * bltzal_op, bgezal_op, bltzall_op, bgezall_op.
                 */
        case bcond_op:
                switch (insn.i_format.rt) {
                case bltz_op:
                case bltzl_op:
                        if ((long)arch->gprs[insn.i_format.rs] < 0)
                                epc = epc + 4 + (insn.i_format.simmediate << 2);
                        else
                                epc += 8;
                        nextpc = epc;
                        break;

                case bgez_op:
                case bgezl_op:
                        if ((long)arch->gprs[insn.i_format.rs] >= 0)
                                epc = epc + 4 + (insn.i_format.simmediate << 2);
                        else
                                epc += 8;
                        nextpc = epc;
                        break;

                case bltzal_op:
                case bltzall_op:
                        arch->gprs[31] = epc + 8;
                        if ((long)arch->gprs[insn.i_format.rs] < 0)
                                epc = epc + 4 + (insn.i_format.simmediate << 2);
                        else
                                epc += 8;
                        nextpc = epc;
                        break;

                case bgezal_op:
                case bgezall_op:
                        arch->gprs[31] = epc + 8;
                        if ((long)arch->gprs[insn.i_format.rs] >= 0)
                                epc = epc + 4 + (insn.i_format.simmediate << 2);
                        else
                                epc += 8;
                        nextpc = epc;
                        break;
                case bposge32_op:
                        if (!cpu_has_dsp)
                                goto sigill;

                        dspcontrol = rddsp(0x01);

                        if (dspcontrol >= 32)
                                epc = epc + 4 + (insn.i_format.simmediate << 2);
                        else
                                epc += 8;
                        nextpc = epc;
                        break;
                }
                break;

                /* These are unconditional and in j_format. */
        case jal_op:
                arch->gprs[31] = instpc + 8;
        case j_op:
                epc += 4;
                epc >>= 28;
                epc <<= 28;
                epc |= (insn.j_format.target << 2);
                nextpc = epc;
                break;

                /* These are conditional and in i_format. */
        case beq_op:
        case beql_op:
                if (arch->gprs[insn.i_format.rs] ==
                    arch->gprs[insn.i_format.rt])
                        epc = epc + 4 + (insn.i_format.simmediate << 2);
                else
                        epc += 8;
                nextpc = epc;
                break;

        case bne_op:
        case bnel_op:
                if (arch->gprs[insn.i_format.rs] !=
                    arch->gprs[insn.i_format.rt])
                        epc = epc + 4 + (insn.i_format.simmediate << 2);
                else
                        epc += 8;
                nextpc = epc;
                break;

        case blez_op:   /* POP06 */
#ifndef CONFIG_CPU_MIPSR6
        case blezl_op:  /* removed in R6 */
#endif
                if (insn.i_format.rt != 0)
                        goto compact_branch;
                if ((long)arch->gprs[insn.i_format.rs] <= 0)
                        epc = epc + 4 + (insn.i_format.simmediate << 2);
                else
                        epc += 8;
                nextpc = epc;
                break;

        case bgtz_op:   /* POP07 */
#ifndef CONFIG_CPU_MIPSR6
        case bgtzl_op:  /* removed in R6 */
#endif
                if (insn.i_format.rt != 0)
                        goto compact_branch;
                if ((long)arch->gprs[insn.i_format.rs] > 0)
                        epc = epc + 4 + (insn.i_format.simmediate << 2);
                else
                        epc += 8;
                nextpc = epc;
                break;

                /* And now the FPA/cp1 branch instructions. */
        case cop1_op:
                kvm_err("%s: unsupported cop1_op\n", __func__);
                break;

#ifdef CONFIG_CPU_MIPSR6
        /* R6 added the following compact branches with forbidden slots */
        case blezl_op:  /* POP26 */
        case bgtzl_op:  /* POP27 */
                /* only rt == 0 isn't compact branch */
                if (insn.i_format.rt != 0)
                        goto compact_branch;
                break;
        case pop10_op:
        case pop30_op:
                /* only rs == rt == 0 is reserved, rest are compact branches */
                if (insn.i_format.rs != 0 || insn.i_format.rt != 0)
                        goto compact_branch;
                break;
        case pop66_op:
        case pop76_op:
                /* only rs == 0 isn't compact branch */
                if (insn.i_format.rs != 0)
                        goto compact_branch;
                break;
compact_branch:
                /*
                 * If we've hit an exception on the forbidden slot, then
                 * the branch must not have been taken.
                 */
                epc += 8;
                nextpc = epc;
                break;
#else
compact_branch:
                /* Compact branches not supported before R6 */
                break;
#endif
        }

        return nextpc;

unaligned:
        kvm_err("%s: unaligned epc\n", __func__);
        return nextpc;

sigill:
        kvm_err("%s: DSP branch but not DSP ASE\n", __func__);
        return nextpc;
}

enum emulation_result update_pc(struct kvm_vcpu *vcpu, u32 cause)
{
        unsigned long branch_pc;
        enum emulation_result er = EMULATE_DONE;

        if (cause & CAUSEF_BD) {
                branch_pc = kvm_compute_return_epc(vcpu, vcpu->arch.pc);
                if (branch_pc == KVM_INVALID_INST) {
                        er = EMULATE_FAIL;
                } else {
                        vcpu->arch.pc = branch_pc;
                        kvm_debug("BD update_pc(): New PC: %#lx\n",
                                  vcpu->arch.pc);
                }
        } else
                vcpu->arch.pc += 4;

        kvm_debug("update_pc(): New PC: %#lx\n", vcpu->arch.pc);

        return er;
}

/**
 * kvm_mips_count_disabled() - Find whether the CP0_Count timer is disabled.
 * @vcpu:       Virtual CPU.
 *
 * Returns:     1 if the CP0_Count timer is disabled by either the guest
 *              CP0_Cause.DC bit or the count_ctl.DC bit.
 *              0 otherwise (in which case CP0_Count timer is running).
 */
static inline int kvm_mips_count_disabled(struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;

        return  (vcpu->arch.count_ctl & KVM_REG_MIPS_COUNT_CTL_DC) ||
                (kvm_read_c0_guest_cause(cop0) & CAUSEF_DC);
}

/**
 * kvm_mips_ktime_to_count() - Scale ktime_t to a 32-bit count.
 *
 * Caches the dynamic nanosecond bias in vcpu->arch.count_dyn_bias.
 *
 * Assumes !kvm_mips_count_disabled(@vcpu) (guest CP0_Count timer is running).
 */
static u32 kvm_mips_ktime_to_count(struct kvm_vcpu *vcpu, ktime_t now)
{
        s64 now_ns, periods;
        u64 delta;

        now_ns = ktime_to_ns(now);
        delta = now_ns + vcpu->arch.count_dyn_bias;

        if (delta >= vcpu->arch.count_period) {
                /* If delta is out of safe range the bias needs adjusting */
                periods = div64_s64(now_ns, vcpu->arch.count_period);
                vcpu->arch.count_dyn_bias = -periods * vcpu->arch.count_period;
                /* Recalculate delta with new bias */
                delta = now_ns + vcpu->arch.count_dyn_bias;
        }

        /*
         * We've ensured that:
         *   delta < count_period
         *
         * Therefore the intermediate delta*count_hz will never overflow since
         * at the boundary condition:
         *   delta = count_period
         *   delta = NSEC_PER_SEC * 2^32 / count_hz
         *   delta * count_hz = NSEC_PER_SEC * 2^32
         */
        return div_u64(delta * vcpu->arch.count_hz, NSEC_PER_SEC);
}

/**
 * kvm_mips_count_time() - Get effective current time.
 * @vcpu:       Virtual CPU.
 *
 * Get effective monotonic ktime. This is usually a straightforward ktime_get(),
 * except when the master disable bit is set in count_ctl, in which case it is
 * count_resume, i.e. the time that the count was disabled.
 *
 * Returns:     Effective monotonic ktime for CP0_Count.
 */
static inline ktime_t kvm_mips_count_time(struct kvm_vcpu *vcpu)
{
        if (unlikely(vcpu->arch.count_ctl & KVM_REG_MIPS_COUNT_CTL_DC))
                return vcpu->arch.count_resume;

        return ktime_get();
}

/**
 * kvm_mips_read_count_running() - Read the current count value as if running.
 * @vcpu:       Virtual CPU.
 * @now:        Kernel time to read CP0_Count at.
 *
 * Returns the current guest CP0_Count register at time @now and handles if the
 * timer interrupt is pending and hasn't been handled yet.
 *
 * Returns:     The current value of the guest CP0_Count register.
 */
static u32 kvm_mips_read_count_running(struct kvm_vcpu *vcpu, ktime_t now)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        ktime_t expires, threshold;
        u32 count, compare;
        int running;

        /* Calculate the biased and scaled guest CP0_Count */
        count = vcpu->arch.count_bias + kvm_mips_ktime_to_count(vcpu, now);
        compare = kvm_read_c0_guest_compare(cop0);

        /*
         * Find whether CP0_Count has reached the closest timer interrupt. If
         * not, we shouldn't inject it.
         */
        if ((s32)(count - compare) < 0)
                return count;

        /*
         * The CP0_Count we're going to return has already reached the closest
         * timer interrupt. Quickly check if it really is a new interrupt by
         * looking at whether the interval until the hrtimer expiry time is
         * less than 1/4 of the timer period.
         */
        expires = hrtimer_get_expires(&vcpu->arch.comparecount_timer);
        threshold = ktime_add_ns(now, vcpu->arch.count_period / 4);
        if (ktime_before(expires, threshold)) {
                /*
                 * Cancel it while we handle it so there's no chance of
                 * interference with the timeout handler.
                 */
                running = hrtimer_cancel(&vcpu->arch.comparecount_timer);

                /* Nothing should be waiting on the timeout */
                kvm_mips_callbacks->queue_timer_int(vcpu);

                /*
                 * Restart the timer if it was running based on the expiry time
                 * we read, so that we don't push it back 2 periods.
                 */
                if (running) {
                        expires = ktime_add_ns(expires,
                                               vcpu->arch.count_period);
                        hrtimer_start(&vcpu->arch.comparecount_timer, expires,
                                      HRTIMER_MODE_ABS);
                }
        }

        return count;
}

/**
 * kvm_mips_read_count() - Read the current count value.
 * @vcpu:       Virtual CPU.
 *
 * Read the current guest CP0_Count value, taking into account whether the timer
 * is stopped.
 *
 * Returns:     The current guest CP0_Count value.
 */
u32 kvm_mips_read_count(struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;

        /* If count disabled just read static copy of count */
        if (kvm_mips_count_disabled(vcpu))
                return kvm_read_c0_guest_count(cop0);

        return kvm_mips_read_count_running(vcpu, ktime_get());
}

/**
 * kvm_mips_freeze_hrtimer() - Safely stop the hrtimer.
 * @vcpu:       Virtual CPU.
 * @count:      Output pointer for CP0_Count value at point of freeze.
 *
 * Freeze the hrtimer safely and return both the ktime and the CP0_Count value
 * at the point it was frozen. It is guaranteed that any pending interrupts at
 * the point it was frozen are handled, and none after that point.
 *
 * This is useful where the time/CP0_Count is needed in the calculation of the
 * new parameters.
 *
 * Assumes !kvm_mips_count_disabled(@vcpu) (guest CP0_Count timer is running).
 *
 * Returns:     The ktime at the point of freeze.
 */
static ktime_t kvm_mips_freeze_hrtimer(struct kvm_vcpu *vcpu, u32 *count)
{
        ktime_t now;

        /* stop hrtimer before finding time */
        hrtimer_cancel(&vcpu->arch.comparecount_timer);
        now = ktime_get();

        /* find count at this point and handle pending hrtimer */
        *count = kvm_mips_read_count_running(vcpu, now);

        return now;
}

/**
 * kvm_mips_resume_hrtimer() - Resume hrtimer, updating expiry.
 * @vcpu:       Virtual CPU.
 * @now:        ktime at point of resume.
 * @count:      CP0_Count at point of resume.
 *
 * Resumes the timer and updates the timer expiry based on @now and @count.
 * This can be used in conjunction with kvm_mips_freeze_timer() when timer
 * parameters need to be changed.
 *
 * It is guaranteed that a timer interrupt immediately after resume will be
 * handled, but not if CP_Compare is exactly at @count. That case is already
 * handled by kvm_mips_freeze_timer().
 *
 * Assumes !kvm_mips_count_disabled(@vcpu) (guest CP0_Count timer is running).
 */
static void kvm_mips_resume_hrtimer(struct kvm_vcpu *vcpu,
                                    ktime_t now, u32 count)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        u32 compare;
        u64 delta;
        ktime_t expire;

        /* Calculate timeout (wrap 0 to 2^32) */
        compare = kvm_read_c0_guest_compare(cop0);
        delta = (u64)(u32)(compare - count - 1) + 1;
        delta = div_u64(delta * NSEC_PER_SEC, vcpu->arch.count_hz);
        expire = ktime_add_ns(now, delta);

        /* Update hrtimer to use new timeout */
        hrtimer_cancel(&vcpu->arch.comparecount_timer);
        hrtimer_start(&vcpu->arch.comparecount_timer, expire, HRTIMER_MODE_ABS);
}

/**
 * kvm_mips_write_count() - Modify the count and update timer.
 * @vcpu:       Virtual CPU.
 * @count:      Guest CP0_Count value to set.
 *
 * Sets the CP0_Count value and updates the timer accordingly.
 */
void kvm_mips_write_count(struct kvm_vcpu *vcpu, u32 count)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        ktime_t now;

        /* Calculate bias */
        now = kvm_mips_count_time(vcpu);
        vcpu->arch.count_bias = count - kvm_mips_ktime_to_count(vcpu, now);

        if (kvm_mips_count_disabled(vcpu))
                /* The timer's disabled, adjust the static count */
                kvm_write_c0_guest_count(cop0, count);
        else
                /* Update timeout */
                kvm_mips_resume_hrtimer(vcpu, now, count);
}

/**
 * kvm_mips_init_count() - Initialise timer.
 * @vcpu:       Virtual CPU.
 *
 * Initialise the timer to a sensible frequency, namely 100MHz, zero it, and set
 * it going if it's enabled.
 */
void kvm_mips_init_count(struct kvm_vcpu *vcpu)
{
        /* 100 MHz */
        vcpu->arch.count_hz = 100*1000*1000;
        vcpu->arch.count_period = div_u64((u64)NSEC_PER_SEC << 32,
                                          vcpu->arch.count_hz);
        vcpu->arch.count_dyn_bias = 0;

        /* Starting at 0 */
        kvm_mips_write_count(vcpu, 0);
}

/**
 * kvm_mips_set_count_hz() - Update the frequency of the timer.
 * @vcpu:       Virtual CPU.
 * @count_hz:   Frequency of CP0_Count timer in Hz.
 *
 * Change the frequency of the CP0_Count timer. This is done atomically so that
 * CP0_Count is continuous and no timer interrupt is lost.
 *
 * Returns:     -EINVAL if @count_hz is out of range.
 *              0 on success.
 */
int kvm_mips_set_count_hz(struct kvm_vcpu *vcpu, s64 count_hz)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        int dc;
        ktime_t now;
        u32 count;

        /* ensure the frequency is in a sensible range... */
        if (count_hz <= 0 || count_hz > NSEC_PER_SEC)
                return -EINVAL;
        /* ... and has actually changed */
        if (vcpu->arch.count_hz == count_hz)
                return 0;

        /* Safely freeze timer so we can keep it continuous */
        dc = kvm_mips_count_disabled(vcpu);
        if (dc) {
                now = kvm_mips_count_time(vcpu);
                count = kvm_read_c0_guest_count(cop0);
        } else {
                now = kvm_mips_freeze_hrtimer(vcpu, &count);
        }

        /* Update the frequency */
        vcpu->arch.count_hz = count_hz;
        vcpu->arch.count_period = div_u64((u64)NSEC_PER_SEC << 32, count_hz);
        vcpu->arch.count_dyn_bias = 0;

        /* Calculate adjusted bias so dynamic count is unchanged */
        vcpu->arch.count_bias = count - kvm_mips_ktime_to_count(vcpu, now);

        /* Update and resume hrtimer */
        if (!dc)
                kvm_mips_resume_hrtimer(vcpu, now, count);
        return 0;
}

/**
 * kvm_mips_write_compare() - Modify compare and update timer.
 * @vcpu:       Virtual CPU.
 * @compare:    New CP0_Compare value.
 * @ack:        Whether to acknowledge timer interrupt.
 *
 * Update CP0_Compare to a new value and update the timeout.
 * If @ack, atomically acknowledge any pending timer interrupt, otherwise ensure
 * any pending timer interrupt is preserved.
 */
void kvm_mips_write_compare(struct kvm_vcpu *vcpu, u32 compare, bool ack)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        int dc;
        u32 old_compare = kvm_read_c0_guest_compare(cop0);
        ktime_t now;
        u32 count;

        /* if unchanged, must just be an ack */
        if (old_compare == compare) {
                if (!ack)
                        return;
                kvm_mips_callbacks->dequeue_timer_int(vcpu);
                kvm_write_c0_guest_compare(cop0, compare);
                return;
        }

        /* freeze_hrtimer() takes care of timer interrupts <= count */
        dc = kvm_mips_count_disabled(vcpu);
        if (!dc)
                now = kvm_mips_freeze_hrtimer(vcpu, &count);

        if (ack)
                kvm_mips_callbacks->dequeue_timer_int(vcpu);

        kvm_write_c0_guest_compare(cop0, compare);

        /* resume_hrtimer() takes care of timer interrupts > count */
        if (!dc)
                kvm_mips_resume_hrtimer(vcpu, now, count);
}

/**
 * kvm_mips_count_disable() - Disable count.
 * @vcpu:       Virtual CPU.
 *
 * Disable the CP0_Count timer. A timer interrupt on or before the final stop
 * time will be handled but not after.
 *
 * Assumes CP0_Count was previously enabled but now Guest.CP0_Cause.DC or
 * count_ctl.DC has been set (count disabled).
 *
 * Returns:     The time that the timer was stopped.
 */
static ktime_t kvm_mips_count_disable(struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        u32 count;
        ktime_t now;

        /* Stop hrtimer */
        hrtimer_cancel(&vcpu->arch.comparecount_timer);

        /* Set the static count from the dynamic count, handling pending TI */
        now = ktime_get();
        count = kvm_mips_read_count_running(vcpu, now);
        kvm_write_c0_guest_count(cop0, count);

        return now;
}

/**
 * kvm_mips_count_disable_cause() - Disable count using CP0_Cause.DC.
 * @vcpu:       Virtual CPU.
 *
 * Disable the CP0_Count timer and set CP0_Cause.DC. A timer interrupt on or
 * before the final stop time will be handled if the timer isn't disabled by
 * count_ctl.DC, but not after.
 *
 * Assumes CP0_Cause.DC is clear (count enabled).
 */
void kvm_mips_count_disable_cause(struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;

        kvm_set_c0_guest_cause(cop0, CAUSEF_DC);
        if (!(vcpu->arch.count_ctl & KVM_REG_MIPS_COUNT_CTL_DC))
                kvm_mips_count_disable(vcpu);
}

/**
 * kvm_mips_count_enable_cause() - Enable count using CP0_Cause.DC.
 * @vcpu:       Virtual CPU.
 *
 * Enable the CP0_Count timer and clear CP0_Cause.DC. A timer interrupt after
 * the start time will be handled if the timer isn't disabled by count_ctl.DC,
 * potentially before even returning, so the caller should be careful with
 * ordering of CP0_Cause modifications so as not to lose it.
 *
 * Assumes CP0_Cause.DC is set (count disabled).
 */
void kvm_mips_count_enable_cause(struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        u32 count;

        kvm_clear_c0_guest_cause(cop0, CAUSEF_DC);

        /*
         * Set the dynamic count to match the static count.
         * This starts the hrtimer if count_ctl.DC allows it.
         * Otherwise it conveniently updates the biases.
         */
        count = kvm_read_c0_guest_count(cop0);
        kvm_mips_write_count(vcpu, count);
}

/**
 * kvm_mips_set_count_ctl() - Update the count control KVM register.
 * @vcpu:       Virtual CPU.
 * @count_ctl:  Count control register new value.
 *
 * Set the count control KVM register. The timer is updated accordingly.
 *
 * Returns:     -EINVAL if reserved bits are set.
 *              0 on success.
 */
int kvm_mips_set_count_ctl(struct kvm_vcpu *vcpu, s64 count_ctl)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        s64 changed = count_ctl ^ vcpu->arch.count_ctl;
        s64 delta;
        ktime_t expire, now;
        u32 count, compare;

        /* Only allow defined bits to be changed */
        if (changed & ~(s64)(KVM_REG_MIPS_COUNT_CTL_DC))
                return -EINVAL;

        /* Apply new value */
        vcpu->arch.count_ctl = count_ctl;

        /* Master CP0_Count disable */
        if (changed & KVM_REG_MIPS_COUNT_CTL_DC) {
                /* Is CP0_Cause.DC already disabling CP0_Count? */
                if (kvm_read_c0_guest_cause(cop0) & CAUSEF_DC) {
                        if (count_ctl & KVM_REG_MIPS_COUNT_CTL_DC)
                                /* Just record the current time */
                                vcpu->arch.count_resume = ktime_get();
                } else if (count_ctl & KVM_REG_MIPS_COUNT_CTL_DC) {
                        /* disable timer and record current time */
                        vcpu->arch.count_resume = kvm_mips_count_disable(vcpu);
                } else {
                        /*
                         * Calculate timeout relative to static count at resume
                         * time (wrap 0 to 2^32).
                         */
                        count = kvm_read_c0_guest_count(cop0);
                        compare = kvm_read_c0_guest_compare(cop0);
                        delta = (u64)(u32)(compare - count - 1) + 1;
                        delta = div_u64(delta * NSEC_PER_SEC,
                                        vcpu->arch.count_hz);
                        expire = ktime_add_ns(vcpu->arch.count_resume, delta);

                        /* Handle pending interrupt */
                        now = ktime_get();
                        if (ktime_compare(now, expire) >= 0)
                                /* Nothing should be waiting on the timeout */
                                kvm_mips_callbacks->queue_timer_int(vcpu);

                        /* Resume hrtimer without changing bias */
                        count = kvm_mips_read_count_running(vcpu, now);
                        kvm_mips_resume_hrtimer(vcpu, now, count);
                }
        }

        return 0;
}

/**
 * kvm_mips_set_count_resume() - Update the count resume KVM register.
 * @vcpu:               Virtual CPU.
 * @count_resume:       Count resume register new value.
 *
 * Set the count resume KVM register.
 *
 * Returns:     -EINVAL if out of valid range (0..now).
 *              0 on success.
 */
int kvm_mips_set_count_resume(struct kvm_vcpu *vcpu, s64 count_resume)
{
        /*
         * It doesn't make sense for the resume time to be in the future, as it
         * would be possible for the next interrupt to be more than a full
         * period in the future.
         */
        if (count_resume < 0 || count_resume > ktime_to_ns(ktime_get()))
                return -EINVAL;

        vcpu->arch.count_resume = ns_to_ktime(count_resume);
        return 0;
}

/**
 * kvm_mips_count_timeout() - Push timer forward on timeout.
 * @vcpu:       Virtual CPU.
 *
 * Handle an hrtimer event by push the hrtimer forward a period.
 *
 * Returns:     The hrtimer_restart value to return to the hrtimer subsystem.
 */
enum hrtimer_restart kvm_mips_count_timeout(struct kvm_vcpu *vcpu)
{
        /* Add the Count period to the current expiry time */
        hrtimer_add_expires_ns(&vcpu->arch.comparecount_timer,
                               vcpu->arch.count_period);
        return HRTIMER_RESTART;
}

enum emulation_result kvm_mips_emul_eret(struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        enum emulation_result er = EMULATE_DONE;

        if (kvm_read_c0_guest_status(cop0) & ST0_EXL) {
                kvm_debug("[%#lx] ERET to %#lx\n", vcpu->arch.pc,
                          kvm_read_c0_guest_epc(cop0));
                kvm_clear_c0_guest_status(cop0, ST0_EXL);
                vcpu->arch.pc = kvm_read_c0_guest_epc(cop0);

        } else if (kvm_read_c0_guest_status(cop0) & ST0_ERL) {
                kvm_clear_c0_guest_status(cop0, ST0_ERL);
                vcpu->arch.pc = kvm_read_c0_guest_errorepc(cop0);
        } else {
                kvm_err("[%#lx] ERET when MIPS_SR_EXL|MIPS_SR_ERL == 0\n",
                        vcpu->arch.pc);
                er = EMULATE_FAIL;
        }

        return er;
}

enum emulation_result kvm_mips_emul_wait(struct kvm_vcpu *vcpu)
{
        kvm_debug("[%#lx] !!!WAIT!!! (%#lx)\n", vcpu->arch.pc,
                  vcpu->arch.pending_exceptions);

        ++vcpu->stat.wait_exits;
        trace_kvm_exit(vcpu, KVM_TRACE_EXIT_WAIT);
        if (!vcpu->arch.pending_exceptions) {
                vcpu->arch.wait = 1;
                kvm_vcpu_block(vcpu);

                /*
                 * We we are runnable, then definitely go off to user space to
                 * check if any I/O interrupts are pending.
                 */
                if (kvm_check_request(KVM_REQ_UNHALT, vcpu)) {
                        clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
                        vcpu->run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
                }
        }

        return EMULATE_DONE;
}

/*
 * XXXKYMA: Linux doesn't seem to use TLBR, return EMULATE_FAIL for now so that
 * we can catch this, if things ever change
 */
enum emulation_result kvm_mips_emul_tlbr(struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        unsigned long pc = vcpu->arch.pc;

        kvm_err("[%#lx] COP0_TLBR [%ld]\n", pc, kvm_read_c0_guest_index(cop0));
        return EMULATE_FAIL;
}

/* Write Guest TLB Entry @ Index */
enum emulation_result kvm_mips_emul_tlbwi(struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        int index = kvm_read_c0_guest_index(cop0);
        struct kvm_mips_tlb *tlb = NULL;
        unsigned long pc = vcpu->arch.pc;

        if (index < 0 || index >= KVM_MIPS_GUEST_TLB_SIZE) {
                kvm_debug("%s: illegal index: %d\n", __func__, index);
                kvm_debug("[%#lx] COP0_TLBWI [%d] (entryhi: %#lx, entrylo0: %#lx entrylo1: %#lx, mask: %#lx)\n",
                          pc, index, kvm_read_c0_guest_entryhi(cop0),
                          kvm_read_c0_guest_entrylo0(cop0),
                          kvm_read_c0_guest_entrylo1(cop0),
                          kvm_read_c0_guest_pagemask(cop0));
                index = (index & ~0x80000000) % KVM_MIPS_GUEST_TLB_SIZE;
        }

        tlb = &vcpu->arch.guest_tlb[index];
        /*
         * Probe the shadow host TLB for the entry being overwritten, if one
         * matches, invalidate it
         */
        kvm_mips_host_tlb_inv(vcpu, tlb->tlb_hi);

        tlb->tlb_mask = kvm_read_c0_guest_pagemask(cop0);
        tlb->tlb_hi = kvm_read_c0_guest_entryhi(cop0);
        tlb->tlb_lo[0] = kvm_read_c0_guest_entrylo0(cop0);
        tlb->tlb_lo[1] = kvm_read_c0_guest_entrylo1(cop0);

        kvm_debug("[%#lx] COP0_TLBWI [%d] (entryhi: %#lx, entrylo0: %#lx entrylo1: %#lx, mask: %#lx)\n",
                  pc, index, kvm_read_c0_guest_entryhi(cop0),
                  kvm_read_c0_guest_entrylo0(cop0),
                  kvm_read_c0_guest_entrylo1(cop0),
                  kvm_read_c0_guest_pagemask(cop0));

        return EMULATE_DONE;
}

/* Write Guest TLB Entry @ Random Index */
enum emulation_result kvm_mips_emul_tlbwr(struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_mips_tlb *tlb = NULL;
        unsigned long pc = vcpu->arch.pc;
        int index;

        get_random_bytes(&index, sizeof(index));
        index &= (KVM_MIPS_GUEST_TLB_SIZE - 1);

        tlb = &vcpu->arch.guest_tlb[index];

        /*
         * Probe the shadow host TLB for the entry being overwritten, if one
         * matches, invalidate it
         */
        kvm_mips_host_tlb_inv(vcpu, tlb->tlb_hi);

        tlb->tlb_mask = kvm_read_c0_guest_pagemask(cop0);
        tlb->tlb_hi = kvm_read_c0_guest_entryhi(cop0);
        tlb->tlb_lo[0] = kvm_read_c0_guest_entrylo0(cop0);
        tlb->tlb_lo[1] = kvm_read_c0_guest_entrylo1(cop0);

        kvm_debug("[%#lx] COP0_TLBWR[%d] (entryhi: %#lx, entrylo0: %#lx entrylo1: %#lx)\n",
                  pc, index, kvm_read_c0_guest_entryhi(cop0),
                  kvm_read_c0_guest_entrylo0(cop0),
                  kvm_read_c0_guest_entrylo1(cop0));

        return EMULATE_DONE;
}

enum emulation_result kvm_mips_emul_tlbp(struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        long entryhi = kvm_read_c0_guest_entryhi(cop0);
        unsigned long pc = vcpu->arch.pc;
        int index = -1;

        index = kvm_mips_guest_tlb_lookup(vcpu, entryhi);

        kvm_write_c0_guest_index(cop0, index);

        kvm_debug("[%#lx] COP0_TLBP (entryhi: %#lx), index: %d\n", pc, entryhi,
                  index);

        return EMULATE_DONE;
}

/**
 * kvm_mips_config1_wrmask() - Find mask of writable bits in guest Config1
 * @vcpu:       Virtual CPU.
 *
 * Finds the mask of bits which are writable in the guest's Config1 CP0
 * register, by userland (currently read-only to the guest).
 */
unsigned int kvm_mips_config1_wrmask(struct kvm_vcpu *vcpu)
{
        unsigned int mask = 0;

        /* Permit FPU to be present if FPU is supported */
        if (kvm_mips_guest_can_have_fpu(&vcpu->arch))
                mask |= MIPS_CONF1_FP;

        return mask;
}

/**
 * kvm_mips_config3_wrmask() - Find mask of writable bits in guest Config3
 * @vcpu:       Virtual CPU.
 *
 * Finds the mask of bits which are writable in the guest's Config3 CP0
 * register, by userland (currently read-only to the guest).
 */
unsigned int kvm_mips_config3_wrmask(struct kvm_vcpu *vcpu)
{
        /* Config4 and ULRI are optional */
        unsigned int mask = MIPS_CONF_M | MIPS_CONF3_ULRI;

        /* Permit MSA to be present if MSA is supported */
        if (kvm_mips_guest_can_have_msa(&vcpu->arch))
                mask |= MIPS_CONF3_MSA;

        return mask;
}

/**
 * kvm_mips_config4_wrmask() - Find mask of writable bits in guest Config4
 * @vcpu:       Virtual CPU.
 *
 * Finds the mask of bits which are writable in the guest's Config4 CP0
 * register, by userland (currently read-only to the guest).
 */
unsigned int kvm_mips_config4_wrmask(struct kvm_vcpu *vcpu)
{
        /* Config5 is optional */
        unsigned int mask = MIPS_CONF_M;

        /* KScrExist */
        mask |= (unsigned int)vcpu->arch.kscratch_enabled << 16;

        return mask;
}

/**
 * kvm_mips_config5_wrmask() - Find mask of writable bits in guest Config5
 * @vcpu:       Virtual CPU.
 *
 * Finds the mask of bits which are writable in the guest's Config5 CP0
 * register, by the guest itself.
 */
unsigned int kvm_mips_config5_wrmask(struct kvm_vcpu *vcpu)
{

        unsigned int mask = 0;

        /* Permit MSAEn changes if MSA supported and enabled */
        if (kvm_mips_guest_has_msa(&vcpu->arch))
                mask |= MIPS_CONF5_MSAEN;

        /*
         * Permit guest FPU mode changes if FPU is enabled and the relevant
         * feature exists according to FIR register.
         */
        if (kvm_mips_guest_has_fpu(&vcpu->arch)) {
                if (cpu_has_fre)
                        mask |= MIPS_CONF5_FRE;
                /* We don't support UFR or UFE */
        }

        return mask;
}

enum emulation_result kvm_mips_emulate_CP0(union mips_instruction inst,
                                           u32 *opc, u32 cause,
                                           struct kvm_run *run,
                                           struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        enum emulation_result er = EMULATE_DONE;
        u32 rt, rd, sel;
        unsigned long curr_pc;

        /*
         * Update PC and hold onto current PC in case there is
         * an error and we want to rollback the PC
         */
        curr_pc = vcpu->arch.pc;
        er = update_pc(vcpu, cause);
        if (er == EMULATE_FAIL)
                return er;

        if (inst.co_format.co) {
                switch (inst.co_format.func) {
                case tlbr_op:   /*  Read indexed TLB entry  */
                        er = kvm_mips_emul_tlbr(vcpu);
                        break;
                case tlbwi_op:  /*  Write indexed  */
                        er = kvm_mips_emul_tlbwi(vcpu);
                        break;
                case tlbwr_op:  /*  Write random  */
                        er = kvm_mips_emul_tlbwr(vcpu);
                        break;
                case tlbp_op:   /* TLB Probe */
                        er = kvm_mips_emul_tlbp(vcpu);
                        break;
                case rfe_op:
                        kvm_err("!!!COP0_RFE!!!\n");
                        break;
                case eret_op:
                        er = kvm_mips_emul_eret(vcpu);
                        goto dont_update_pc;
                case wait_op:
                        er = kvm_mips_emul_wait(vcpu);
                        break;
                }
        } else {
                rt = inst.c0r_format.rt;
                rd = inst.c0r_format.rd;
                sel = inst.c0r_format.sel;

                switch (inst.c0r_format.rs) {
                case mfc_op:
#ifdef CONFIG_KVM_MIPS_DEBUG_COP0_COUNTERS
                        cop0->stat[rd][sel]++;
#endif
                        /* Get reg */
                        if ((rd == MIPS_CP0_COUNT) && (sel == 0)) {
                                vcpu->arch.gprs[rt] =
                                    (s32)kvm_mips_read_count(vcpu);
                        } else if ((rd == MIPS_CP0_ERRCTL) && (sel == 0)) {
                                vcpu->arch.gprs[rt] = 0x0;
#ifdef CONFIG_KVM_MIPS_DYN_TRANS
                                kvm_mips_trans_mfc0(inst, opc, vcpu);
#endif
                        } else {
                                vcpu->arch.gprs[rt] = (s32)cop0->reg[rd][sel];

#ifdef CONFIG_KVM_MIPS_DYN_TRANS
                                kvm_mips_trans_mfc0(inst, opc, vcpu);
#endif
                        }

                        trace_kvm_hwr(vcpu, KVM_TRACE_MFC0,
                                      KVM_TRACE_COP0(rd, sel),
                                      vcpu->arch.gprs[rt]);
                        break;

                case dmfc_op:
                        vcpu->arch.gprs[rt] = cop0->reg[rd][sel];

                        trace_kvm_hwr(vcpu, KVM_TRACE_DMFC0,
                                      KVM_TRACE_COP0(rd, sel),
                                      vcpu->arch.gprs[rt]);
                        break;

                case mtc_op:
#ifdef CONFIG_KVM_MIPS_DEBUG_COP0_COUNTERS
                        cop0->stat[rd][sel]++;
#endif
                        trace_kvm_hwr(vcpu, KVM_TRACE_MTC0,
                                      KVM_TRACE_COP0(rd, sel),
                                      vcpu->arch.gprs[rt]);

                        if ((rd == MIPS_CP0_TLB_INDEX)
                            && (vcpu->arch.gprs[rt] >=
                                KVM_MIPS_GUEST_TLB_SIZE)) {
                                kvm_err("Invalid TLB Index: %ld",
                                        vcpu->arch.gprs[rt]);
                                er = EMULATE_FAIL;
                                break;
                        }
#define C0_EBASE_CORE_MASK 0xff
                        if ((rd == MIPS_CP0_PRID) && (sel == 1)) {
                                /* Preserve CORE number */
                                kvm_change_c0_guest_ebase(cop0,
                                                          ~(C0_EBASE_CORE_MASK),
                                                          vcpu->arch.gprs[rt]);
                                kvm_err("MTCz, cop0->reg[EBASE]: %#lx\n",
                                        kvm_read_c0_guest_ebase(cop0));
                        } else if (rd == MIPS_CP0_TLB_HI && sel == 0) {
                                u32 nasid =
                                        vcpu->arch.gprs[rt] & KVM_ENTRYHI_ASID;
                                if ((KSEGX(vcpu->arch.gprs[rt]) != CKSEG0) &&
                                    ((kvm_read_c0_guest_entryhi(cop0) &
                                      KVM_ENTRYHI_ASID) != nasid)) {
                                        trace_kvm_asid_change(vcpu,
                                                kvm_read_c0_guest_entryhi(cop0)
                                                        & KVM_ENTRYHI_ASID,
                                                nasid);

                                        /* Blow away the shadow host TLBs */
                                        kvm_mips_flush_host_tlb(1);
                                }
                                kvm_write_c0_guest_entryhi(cop0,
                                                           vcpu->arch.gprs[rt]);
                        }
                        /* Are we writing to COUNT */
                        else if ((rd == MIPS_CP0_COUNT) && (sel == 0)) {
                                kvm_mips_write_count(vcpu, vcpu->arch.gprs[rt]);
                                goto done;
                        } else if ((rd == MIPS_CP0_COMPARE) && (sel == 0)) {
                                /* If we are writing to COMPARE */
                                /* Clear pending timer interrupt, if any */
                                kvm_mips_write_compare(vcpu,
                                                       vcpu->arch.gprs[rt],
                                                       true);
                        } else if ((rd == MIPS_CP0_STATUS) && (sel == 0)) {
                                unsigned int old_val, val, change;

                                old_val = kvm_read_c0_guest_status(cop0);
                                val = vcpu->arch.gprs[rt];
                                change = val ^ old_val;

                                /* Make sure that the NMI bit is never set */
                                val &= ~ST0_NMI;

                                /*
                                 * Don't allow CU1 or FR to be set unless FPU
                                 * capability enabled and exists in guest
                                 * configuration.
                                 */
                                if (!kvm_mips_guest_has_fpu(&vcpu->arch))
                                        val &= ~(ST0_CU1 | ST0_FR);

                                /*
                                 * Also don't allow FR to be set if host doesn't
                                 * support it.
                                 */
                                if (!(current_cpu_data.fpu_id & MIPS_FPIR_F64))
                                        val &= ~ST0_FR;


                                /* Handle changes in FPU mode */
                                preempt_disable();

                                /*
                                 * FPU and Vector register state is made
                                 * UNPREDICTABLE by a change of FR, so don't
                                 * even bother saving it.
                                 */
                                if (change & ST0_FR)
                                        kvm_drop_fpu(vcpu);

                                /*
                                 * If MSA state is already live, it is undefined
                                 * how it interacts with FR=0 FPU state, and we
                                 * don't want to hit reserved instruction
                                 * exceptions trying to save the MSA state later
                                 * when CU=1 && FR=1, so play it safe and save
                                 * it first.
                                 */
                                if (change & ST0_CU1 && !(val & ST0_FR) &&
                                    vcpu->arch.aux_inuse & KVM_MIPS_AUX_MSA)
                                        kvm_lose_fpu(vcpu);

                                /*
                                 * Propagate CU1 (FPU enable) changes
                                 * immediately if the FPU context is already
                                 * loaded. When disabling we leave the context
                                 * loaded so it can be quickly enabled again in
                                 * the near future.
                                 */
                                if (change & ST0_CU1 &&
                                    vcpu->arch.aux_inuse & KVM_MIPS_AUX_FPU)
                                        change_c0_status(ST0_CU1, val);

                                preempt_enable();

                                kvm_write_c0_guest_status(cop0, val);

#ifdef CONFIG_KVM_MIPS_DYN_TRANS
                                /*
                                 * If FPU present, we need CU1/FR bits to take
                                 * effect fairly soon.
                                 */
                                if (!kvm_mips_guest_has_fpu(&vcpu->arch))
                                        kvm_mips_trans_mtc0(inst, opc, vcpu);
#endif
                        } else if ((rd == MIPS_CP0_CONFIG) && (sel == 5)) {
                                unsigned int old_val, val, change, wrmask;

                                old_val = kvm_read_c0_guest_config5(cop0);
                                val = vcpu->arch.gprs[rt];

                                /* Only a few bits are writable in Config5 */
                                wrmask = kvm_mips_config5_wrmask(vcpu);
                                change = (val ^ old_val) & wrmask;
                                val = old_val ^ change;


                                /* Handle changes in FPU/MSA modes */
                                preempt_disable();

                                /*
                                 * Propagate FRE changes immediately if the FPU
                                 * context is already loaded.
                                 */
                                if (change & MIPS_CONF5_FRE &&
                                    vcpu->arch.aux_inuse & KVM_MIPS_AUX_FPU)
                                        change_c0_config5(MIPS_CONF5_FRE, val);

                                /*
                                 * Propagate MSAEn changes immediately if the
                                 * MSA context is already loaded. When disabling
                                 * we leave the context loaded so it can be
                                 * quickly enabled again in the near future.
                                 */
                                if (change & MIPS_CONF5_MSAEN &&
                                    vcpu->arch.aux_inuse & KVM_MIPS_AUX_MSA)
                                        change_c0_config5(MIPS_CONF5_MSAEN,
                                                          val);

                                preempt_enable();

                                kvm_write_c0_guest_config5(cop0, val);
                        } else if ((rd == MIPS_CP0_CAUSE) && (sel == 0)) {
                                u32 old_cause, new_cause;

                                old_cause = kvm_read_c0_guest_cause(cop0);
                                new_cause = vcpu->arch.gprs[rt];
                                /* Update R/W bits */
                                kvm_change_c0_guest_cause(cop0, 0x08800300,
                                                          new_cause);
                                /* DC bit enabling/disabling timer? */
                                if ((old_cause ^ new_cause) & CAUSEF_DC) {
                                        if (new_cause & CAUSEF_DC)
                                                kvm_mips_count_disable_cause(vcpu);
                                        else
                                                kvm_mips_count_enable_cause(vcpu);
                                }
                        } else if ((rd == MIPS_CP0_HWRENA) && (sel == 0)) {
                                u32 mask = MIPS_HWRENA_CPUNUM |
                                           MIPS_HWRENA_SYNCISTEP |
                                           MIPS_HWRENA_CC |
                                           MIPS_HWRENA_CCRES;

                                if (kvm_read_c0_guest_config3(cop0) &
                                    MIPS_CONF3_ULRI)
                                        mask |= MIPS_HWRENA_ULR;
                                cop0->reg[rd][sel] = vcpu->arch.gprs[rt] & mask;
                        } else {
                                cop0->reg[rd][sel] = vcpu->arch.gprs[rt];
#ifdef CONFIG_KVM_MIPS_DYN_TRANS
                                kvm_mips_trans_mtc0(inst, opc, vcpu);
#endif
                        }
                        break;

                case dmtc_op:
                        kvm_err("!!!!!!![%#lx]dmtc_op: rt: %d, rd: %d, sel: %d!!!!!!\n",
                                vcpu->arch.pc, rt, rd, sel);
                        trace_kvm_hwr(vcpu, KVM_TRACE_DMTC0,
                                      KVM_TRACE_COP0(rd, sel),
                                      vcpu->arch.gprs[rt]);
                        er = EMULATE_FAIL;
                        break;

                case mfmc0_op:
#ifdef KVM_MIPS_DEBUG_COP0_COUNTERS
                        cop0->stat[MIPS_CP0_STATUS][0]++;
#endif
                        if (rt != 0)
                                vcpu->arch.gprs[rt] =
                                    kvm_read_c0_guest_status(cop0);
                        /* EI */
                        if (inst.mfmc0_format.sc) {
                                kvm_debug("[%#lx] mfmc0_op: EI\n",
                                          vcpu->arch.pc);
                                kvm_set_c0_guest_status(cop0, ST0_IE);
                        } else {
                                kvm_debug("[%#lx] mfmc0_op: DI\n",
                                          vcpu->arch.pc);
                                kvm_clear_c0_guest_status(cop0, ST0_IE);
                        }

                        break;

                case wrpgpr_op:
                        {
                                u32 css = cop0->reg[MIPS_CP0_STATUS][2] & 0xf;
                                u32 pss =
                                    (cop0->reg[MIPS_CP0_STATUS][2] >> 6) & 0xf;
                                /*
                                 * We don't support any shadow register sets, so
                                 * SRSCtl[PSS] == SRSCtl[CSS] = 0
                                 */
                                if (css || pss) {
                                        er = EMULATE_FAIL;
                                        break;
                                }
                                kvm_debug("WRPGPR[%d][%d] = %#lx\n", pss, rd,
                                          vcpu->arch.gprs[rt]);
                                vcpu->arch.gprs[rd] = vcpu->arch.gprs[rt];
                        }
                        break;
                default:
                        kvm_err("[%#lx]MachEmulateCP0: unsupported COP0, copz: 0x%x\n",
                                vcpu->arch.pc, inst.c0r_format.rs);
                        er = EMULATE_FAIL;
                        break;
                }
        }

done:
        /* Rollback PC only if emulation was unsuccessful */
        if (er == EMULATE_FAIL)
                vcpu->arch.pc = curr_pc;

dont_update_pc:
        /*
         * This is for special instructions whose emulation
         * updates the PC, so do not overwrite the PC under
         * any circumstances
         */

        return er;
}

enum emulation_result kvm_mips_emulate_store(union mips_instruction inst,
                                             u32 cause,
                                             struct kvm_run *run,
                                             struct kvm_vcpu *vcpu)
{
        enum emulation_result er = EMULATE_DO_MMIO;
        u32 rt;
        u32 bytes;
        void *data = run->mmio.data;
        unsigned long curr_pc;

        /*
         * Update PC and hold onto current PC in case there is
         * an error and we want to rollback the PC
         */
        curr_pc = vcpu->arch.pc;
        er = update_pc(vcpu, cause);
        if (er == EMULATE_FAIL)
                return er;

        rt = inst.i_format.rt;

        switch (inst.i_format.opcode) {
        case sb_op:
                bytes = 1;
                if (bytes > sizeof(run->mmio.data)) {
                        kvm_err("%s: bad MMIO length: %d\n", __func__,
                               run->mmio.len);
                }
                run->mmio.phys_addr =
                    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
                                                   host_cp0_badvaddr);
                if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
                        er = EMULATE_FAIL;
                        break;
                }
                run->mmio.len = bytes;
                run->mmio.is_write = 1;
                vcpu->mmio_needed = 1;
                vcpu->mmio_is_write = 1;
                *(u8 *) data = vcpu->arch.gprs[rt];
                kvm_debug("OP_SB: eaddr: %#lx, gpr: %#lx, data: %#x\n",
                          vcpu->arch.host_cp0_badvaddr, vcpu->arch.gprs[rt],
                          *(u8 *) data);

                break;

        case sw_op:
                bytes = 4;
                if (bytes > sizeof(run->mmio.data)) {
                        kvm_err("%s: bad MMIO length: %d\n", __func__,
                               run->mmio.len);
                }
                run->mmio.phys_addr =
                    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
                                                   host_cp0_badvaddr);
                if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
                        er = EMULATE_FAIL;
                        break;
                }

                run->mmio.len = bytes;
                run->mmio.is_write = 1;
                vcpu->mmio_needed = 1;
                vcpu->mmio_is_write = 1;
                *(u32 *) data = vcpu->arch.gprs[rt];

                kvm_debug("[%#lx] OP_SW: eaddr: %#lx, gpr: %#lx, data: %#x\n",
                          vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
                          vcpu->arch.gprs[rt], *(u32 *) data);
                break;

        case sh_op:
                bytes = 2;
                if (bytes > sizeof(run->mmio.data)) {
                        kvm_err("%s: bad MMIO length: %d\n", __func__,
                               run->mmio.len);
                }
                run->mmio.phys_addr =
                    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
                                                   host_cp0_badvaddr);
                if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
                        er = EMULATE_FAIL;
                        break;
                }

                run->mmio.len = bytes;
                run->mmio.is_write = 1;
                vcpu->mmio_needed = 1;
                vcpu->mmio_is_write = 1;
                *(u16 *) data = vcpu->arch.gprs[rt];

                kvm_debug("[%#lx] OP_SH: eaddr: %#lx, gpr: %#lx, data: %#x\n",
                          vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
                          vcpu->arch.gprs[rt], *(u32 *) data);
                break;

        default:
                kvm_err("Store not yet supported (inst=0x%08x)\n",
                        inst.word);
                er = EMULATE_FAIL;
                break;
        }

        /* Rollback PC if emulation was unsuccessful */
        if (er == EMULATE_FAIL)
                vcpu->arch.pc = curr_pc;

        return er;
}

enum emulation_result kvm_mips_emulate_load(union mips_instruction inst,
                                            u32 cause, struct kvm_run *run,
                                            struct kvm_vcpu *vcpu)
{
        enum emulation_result er = EMULATE_DO_MMIO;
        u32 op, rt;
        u32 bytes;

        rt = inst.i_format.rt;
        op = inst.i_format.opcode;

        vcpu->arch.pending_load_cause = cause;
        vcpu->arch.io_gpr = rt;

        switch (op) {
        case lw_op:
                bytes = 4;
                if (bytes > sizeof(run->mmio.data)) {
                        kvm_err("%s: bad MMIO length: %d\n", __func__,
                               run->mmio.len);
                        er = EMULATE_FAIL;
                        break;
                }
                run->mmio.phys_addr =
                    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
                                                   host_cp0_badvaddr);
                if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
                        er = EMULATE_FAIL;
                        break;
                }

                run->mmio.len = bytes;
                run->mmio.is_write = 0;
                vcpu->mmio_needed = 1;
                vcpu->mmio_is_write = 0;
                break;

        case lh_op:
        case lhu_op:
                bytes = 2;
                if (bytes > sizeof(run->mmio.data)) {
                        kvm_err("%s: bad MMIO length: %d\n", __func__,
                               run->mmio.len);
                        er = EMULATE_FAIL;
                        break;
                }
                run->mmio.phys_addr =
                    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
                                                   host_cp0_badvaddr);
                if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
                        er = EMULATE_FAIL;
                        break;
                }

                run->mmio.len = bytes;
                run->mmio.is_write = 0;
                vcpu->mmio_needed = 1;
                vcpu->mmio_is_write = 0;

                if (op == lh_op)
                        vcpu->mmio_needed = 2;
                else
                        vcpu->mmio_needed = 1;

                break;

        case lbu_op:
        case lb_op:
                bytes = 1;
                if (bytes > sizeof(run->mmio.data)) {
                        kvm_err("%s: bad MMIO length: %d\n", __func__,
                               run->mmio.len);
                        er = EMULATE_FAIL;
                        break;
                }
                run->mmio.phys_addr =
                    kvm_mips_callbacks->gva_to_gpa(vcpu->arch.
                                                   host_cp0_badvaddr);
                if (run->mmio.phys_addr == KVM_INVALID_ADDR) {
                        er = EMULATE_FAIL;
                        break;
                }

                run->mmio.len = bytes;
                run->mmio.is_write = 0;
                vcpu->mmio_is_write = 0;

                if (op == lb_op)
                        vcpu->mmio_needed = 2;
                else
                        vcpu->mmio_needed = 1;

                break;

        default:
                kvm_err("Load not yet supported (inst=0x%08x)\n",
                        inst.word);
                er = EMULATE_FAIL;
                break;
        }

        return er;
}

enum emulation_result kvm_mips_emulate_cache(union mips_instruction inst,
                                             u32 *opc, u32 cause,
                                             struct kvm_run *run,
                                             struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        enum emulation_result er = EMULATE_DONE;
        u32 cache, op_inst, op, base;
        s16 offset;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        unsigned long va;
        unsigned long curr_pc;

        /*
         * Update PC and hold onto current PC in case there is
         * an error and we want to rollback the PC
         */
        curr_pc = vcpu->arch.pc;
        er = update_pc(vcpu, cause);
        if (er == EMULATE_FAIL)
                return er;

        base = inst.i_format.rs;
        op_inst = inst.i_format.rt;
        if (cpu_has_mips_r6)
                offset = inst.spec3_format.simmediate;
        else
                offset = inst.i_format.simmediate;
        cache = op_inst & CacheOp_Cache;
        op = op_inst & CacheOp_Op;

        va = arch->gprs[base] + offset;

        kvm_debug("CACHE (cache: %#x, op: %#x, base[%d]: %#lx, offset: %#x\n",
                  cache, op, base, arch->gprs[base], offset);

        /*
         * Treat INDEX_INV as a nop, basically issued by Linux on startup to
         * invalidate the caches entirely by stepping through all the
         * ways/indexes
         */
        if (op == Index_Writeback_Inv) {
                kvm_debug("@ %#lx/%#lx CACHE (cache: %#x, op: %#x, base[%d]: %#lx, offset: %#x\n",
                          vcpu->arch.pc, vcpu->arch.gprs[31], cache, op, base,
                          arch->gprs[base], offset);

                if (cache == Cache_D)
                        r4k_blast_dcache();
                else if (cache == Cache_I)
                        r4k_blast_icache();
                else {
                        kvm_err("%s: unsupported CACHE INDEX operation\n",
                                __func__);
                        return EMULATE_FAIL;
                }

#ifdef CONFIG_KVM_MIPS_DYN_TRANS
                kvm_mips_trans_cache_index(inst, opc, vcpu);
#endif
                goto done;
        }

        preempt_disable();
        if (KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG0) {
                if (kvm_mips_host_tlb_lookup(vcpu, va) < 0 &&
                    kvm_mips_handle_kseg0_tlb_fault(va, vcpu)) {
                        kvm_err("%s: handling mapped kseg0 tlb fault for %lx, vcpu: %p, ASID: %#lx\n",
                                __func__, va, vcpu, read_c0_entryhi());
                        er = EMULATE_FAIL;
                        preempt_enable();
                        goto done;
                }
        } else if ((KVM_GUEST_KSEGX(va) < KVM_GUEST_KSEG0) ||
                   KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG23) {
                int index;

                /* If an entry already exists then skip */
                if (kvm_mips_host_tlb_lookup(vcpu, va) >= 0)
                        goto skip_fault;

                /*
                 * If address not in the guest TLB, then give the guest a fault,
                 * the resulting handler will do the right thing
                 */
                index = kvm_mips_guest_tlb_lookup(vcpu, (va & VPN2_MASK) |
                                                  (kvm_read_c0_guest_entryhi
                                                   (cop0) & KVM_ENTRYHI_ASID));

                if (index < 0) {
                        vcpu->arch.host_cp0_badvaddr = va;
                        vcpu->arch.pc = curr_pc;
                        er = kvm_mips_emulate_tlbmiss_ld(cause, NULL, run,
                                                         vcpu);
                        preempt_enable();
                        goto dont_update_pc;
                } else {
                        struct kvm_mips_tlb *tlb = &vcpu->arch.guest_tlb[index];
                        /*
                         * Check if the entry is valid, if not then setup a TLB
                         * invalid exception to the guest
                         */
                        if (!TLB_IS_VALID(*tlb, va)) {
                                vcpu->arch.host_cp0_badvaddr = va;
                                vcpu->arch.pc = curr_pc;
                                er = kvm_mips_emulate_tlbinv_ld(cause, NULL,
                                                                run, vcpu);
                                preempt_enable();
                                goto dont_update_pc;
                        }
                        /*
                         * We fault an entry from the guest tlb to the
                         * shadow host TLB
                         */
                        if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb)) {
                                kvm_err("%s: handling mapped seg tlb fault for %lx, index: %u, vcpu: %p, ASID: %#lx\n",
                                        __func__, va, index, vcpu,
                                        read_c0_entryhi());
                                er = EMULATE_FAIL;
                                preempt_enable();
                                goto done;
                        }
                }
        } else {
                kvm_err("INVALID CACHE INDEX/ADDRESS (cache: %#x, op: %#x, base[%d]: %#lx, offset: %#x\n",
                        cache, op, base, arch->gprs[base], offset);
                er = EMULATE_FAIL;
                preempt_enable();
                goto done;

        }

skip_fault:
        /* XXXKYMA: Only a subset of cache ops are supported, used by Linux */
        if (op_inst == Hit_Writeback_Inv_D || op_inst == Hit_Invalidate_D) {
                flush_dcache_line(va);

#ifdef CONFIG_KVM_MIPS_DYN_TRANS
                /*
                 * Replace the CACHE instruction, with a SYNCI, not the same,
                 * but avoids a trap
                 */
                kvm_mips_trans_cache_va(inst, opc, vcpu);
#endif
        } else if (op_inst == Hit_Invalidate_I) {
                flush_dcache_line(va);
                flush_icache_line(va);

#ifdef CONFIG_KVM_MIPS_DYN_TRANS
                /* Replace the CACHE instruction, with a SYNCI */
                kvm_mips_trans_cache_va(inst, opc, vcpu);
#endif
        } else {
                kvm_err("NO-OP CACHE (cache: %#x, op: %#x, base[%d]: %#lx, offset: %#x\n",
                        cache, op, base, arch->gprs[base], offset);
                er = EMULATE_FAIL;
        }

        preempt_enable();
done:
        /* Rollback PC only if emulation was unsuccessful */
        if (er == EMULATE_FAIL)
                vcpu->arch.pc = curr_pc;

dont_update_pc:
        /*
         * This is for exceptions whose emulation updates the PC, so do not
         * overwrite the PC under any circumstances
         */

        return er;
}

enum emulation_result kvm_mips_emulate_inst(u32 cause, u32 *opc,
                                            struct kvm_run *run,
                                            struct kvm_vcpu *vcpu)
{
        union mips_instruction inst;
        enum emulation_result er = EMULATE_DONE;

        /* Fetch the instruction. */
        if (cause & CAUSEF_BD)
                opc += 1;

        inst.word = kvm_get_inst(opc, vcpu);

        switch (inst.r_format.opcode) {
        case cop0_op:
                er = kvm_mips_emulate_CP0(inst, opc, cause, run, vcpu);
                break;
        case sb_op:
        case sh_op:
        case sw_op:
                er = kvm_mips_emulate_store(inst, cause, run, vcpu);
                break;
        case lb_op:
        case lbu_op:
        case lhu_op:
        case lh_op:
        case lw_op:
                er = kvm_mips_emulate_load(inst, cause, run, vcpu);
                break;

#ifndef CONFIG_CPU_MIPSR6
        case cache_op:
                ++vcpu->stat.cache_exits;
                trace_kvm_exit(vcpu, KVM_TRACE_EXIT_CACHE);
                er = kvm_mips_emulate_cache(inst, opc, cause, run, vcpu);
                break;
#else
        case spec3_op:
                switch (inst.spec3_format.func) {
                case cache6_op:
                        ++vcpu->stat.cache_exits;
                        trace_kvm_exit(vcpu, KVM_TRACE_EXIT_CACHE);
                        er = kvm_mips_emulate_cache(inst, opc, cause, run,
                                                    vcpu);
                        break;
                default:
                        goto unknown;
                };
                break;
unknown:
#endif

        default:
                kvm_err("Instruction emulation not supported (%p/%#x)\n", opc,
                        inst.word);
                kvm_arch_vcpu_dump_regs(vcpu);
                er = EMULATE_FAIL;
                break;
        }

        return er;
}

enum emulation_result kvm_mips_emulate_syscall(u32 cause,
                                               u32 *opc,
                                               struct kvm_run *run,
                                               struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        enum emulation_result er = EMULATE_DONE;

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("Delivering SYSCALL @ pc %#lx\n", arch->pc);

                kvm_change_c0_guest_cause(cop0, (0xff),
                                          (EXCCODE_SYS << CAUSEB_EXCCODE));

                /* Set PC to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x180;

        } else {
                kvm_err("Trying to deliver SYSCALL when EXL is already set\n");
                er = EMULATE_FAIL;
        }

        return er;
}

enum emulation_result kvm_mips_emulate_tlbmiss_ld(u32 cause,
                                                  u32 *opc,
                                                  struct kvm_run *run,
                                                  struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        unsigned long entryhi = (vcpu->arch.  host_cp0_badvaddr & VPN2_MASK) |
                        (kvm_read_c0_guest_entryhi(cop0) & KVM_ENTRYHI_ASID);

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("[EXL == 0] delivering TLB MISS @ pc %#lx\n",
                          arch->pc);

                /* set pc to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x0;

        } else {
                kvm_debug("[EXL == 1] delivering TLB MISS @ pc %#lx\n",
                          arch->pc);

                arch->pc = KVM_GUEST_KSEG0 + 0x180;
        }

        kvm_change_c0_guest_cause(cop0, (0xff),
                                  (EXCCODE_TLBL << CAUSEB_EXCCODE));

        /* setup badvaddr, context and entryhi registers for the guest */
        kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);
        /* XXXKYMA: is the context register used by linux??? */
        kvm_write_c0_guest_entryhi(cop0, entryhi);
        /* Blow away the shadow host TLBs */
        kvm_mips_flush_host_tlb(1);

        return EMULATE_DONE;
}

enum emulation_result kvm_mips_emulate_tlbinv_ld(u32 cause,
                                                 u32 *opc,
                                                 struct kvm_run *run,
                                                 struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        unsigned long entryhi =
                (vcpu->arch.host_cp0_badvaddr & VPN2_MASK) |
                (kvm_read_c0_guest_entryhi(cop0) & KVM_ENTRYHI_ASID);

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("[EXL == 0] delivering TLB INV @ pc %#lx\n",
                          arch->pc);

                /* set pc to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x180;

        } else {
                kvm_debug("[EXL == 1] delivering TLB MISS @ pc %#lx\n",
                          arch->pc);
                arch->pc = KVM_GUEST_KSEG0 + 0x180;
        }

        kvm_change_c0_guest_cause(cop0, (0xff),
                                  (EXCCODE_TLBL << CAUSEB_EXCCODE));

        /* setup badvaddr, context and entryhi registers for the guest */
        kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);
        /* XXXKYMA: is the context register used by linux??? */
        kvm_write_c0_guest_entryhi(cop0, entryhi);
        /* Blow away the shadow host TLBs */
        kvm_mips_flush_host_tlb(1);

        return EMULATE_DONE;
}

enum emulation_result kvm_mips_emulate_tlbmiss_st(u32 cause,
                                                  u32 *opc,
                                                  struct kvm_run *run,
                                                  struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        unsigned long entryhi = (vcpu->arch.host_cp0_badvaddr & VPN2_MASK) |
                        (kvm_read_c0_guest_entryhi(cop0) & KVM_ENTRYHI_ASID);

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("[EXL == 0] Delivering TLB MISS @ pc %#lx\n",
                          arch->pc);

                /* Set PC to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x0;
        } else {
                kvm_debug("[EXL == 1] Delivering TLB MISS @ pc %#lx\n",
                          arch->pc);
                arch->pc = KVM_GUEST_KSEG0 + 0x180;
        }

        kvm_change_c0_guest_cause(cop0, (0xff),
                                  (EXCCODE_TLBS << CAUSEB_EXCCODE));

        /* setup badvaddr, context and entryhi registers for the guest */
        kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);
        /* XXXKYMA: is the context register used by linux??? */
        kvm_write_c0_guest_entryhi(cop0, entryhi);
        /* Blow away the shadow host TLBs */
        kvm_mips_flush_host_tlb(1);

        return EMULATE_DONE;
}

enum emulation_result kvm_mips_emulate_tlbinv_st(u32 cause,
                                                 u32 *opc,
                                                 struct kvm_run *run,
                                                 struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        unsigned long entryhi = (vcpu->arch.host_cp0_badvaddr & VPN2_MASK) |
                (kvm_read_c0_guest_entryhi(cop0) & KVM_ENTRYHI_ASID);

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("[EXL == 0] Delivering TLB MISS @ pc %#lx\n",
                          arch->pc);

                /* Set PC to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x180;
        } else {
                kvm_debug("[EXL == 1] Delivering TLB MISS @ pc %#lx\n",
                          arch->pc);
                arch->pc = KVM_GUEST_KSEG0 + 0x180;
        }

        kvm_change_c0_guest_cause(cop0, (0xff),
                                  (EXCCODE_TLBS << CAUSEB_EXCCODE));

        /* setup badvaddr, context and entryhi registers for the guest */
        kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);
        /* XXXKYMA: is the context register used by linux??? */
        kvm_write_c0_guest_entryhi(cop0, entryhi);
        /* Blow away the shadow host TLBs */
        kvm_mips_flush_host_tlb(1);

        return EMULATE_DONE;
}

/* TLBMOD: store into address matching TLB with Dirty bit off */
enum emulation_result kvm_mips_handle_tlbmod(u32 cause, u32 *opc,
                                             struct kvm_run *run,
                                             struct kvm_vcpu *vcpu)
{
        enum emulation_result er = EMULATE_DONE;
#ifdef DEBUG
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        unsigned long entryhi = (vcpu->arch.host_cp0_badvaddr & VPN2_MASK) |
                        (kvm_read_c0_guest_entryhi(cop0) & KVM_ENTRYHI_ASID);
        int index;

        /* If address not in the guest TLB, then we are in trouble */
        index = kvm_mips_guest_tlb_lookup(vcpu, entryhi);
        if (index < 0) {
                /* XXXKYMA Invalidate and retry */
                kvm_mips_host_tlb_inv(vcpu, vcpu->arch.host_cp0_badvaddr);
                kvm_err("%s: host got TLBMOD for %#lx but entry not present in Guest TLB\n",
                     __func__, entryhi);
                kvm_mips_dump_guest_tlbs(vcpu);
                kvm_mips_dump_host_tlbs();
                return EMULATE_FAIL;
        }
#endif

        er = kvm_mips_emulate_tlbmod(cause, opc, run, vcpu);
        return er;
}

enum emulation_result kvm_mips_emulate_tlbmod(u32 cause,
                                              u32 *opc,
                                              struct kvm_run *run,
                                              struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        unsigned long entryhi = (vcpu->arch.host_cp0_badvaddr & VPN2_MASK) |
                        (kvm_read_c0_guest_entryhi(cop0) & KVM_ENTRYHI_ASID);
        struct kvm_vcpu_arch *arch = &vcpu->arch;

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("[EXL == 0] Delivering TLB MOD @ pc %#lx\n",
                          arch->pc);

                arch->pc = KVM_GUEST_KSEG0 + 0x180;
        } else {
                kvm_debug("[EXL == 1] Delivering TLB MOD @ pc %#lx\n",
                          arch->pc);
                arch->pc = KVM_GUEST_KSEG0 + 0x180;
        }

        kvm_change_c0_guest_cause(cop0, (0xff),
                                  (EXCCODE_MOD << CAUSEB_EXCCODE));

        /* setup badvaddr, context and entryhi registers for the guest */
        kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);
        /* XXXKYMA: is the context register used by linux??? */
        kvm_write_c0_guest_entryhi(cop0, entryhi);
        /* Blow away the shadow host TLBs */
        kvm_mips_flush_host_tlb(1);

        return EMULATE_DONE;
}

enum emulation_result kvm_mips_emulate_fpu_exc(u32 cause,
                                               u32 *opc,
                                               struct kvm_run *run,
                                               struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

        }

        arch->pc = KVM_GUEST_KSEG0 + 0x180;

        kvm_change_c0_guest_cause(cop0, (0xff),
                                  (EXCCODE_CPU << CAUSEB_EXCCODE));
        kvm_change_c0_guest_cause(cop0, (CAUSEF_CE), (0x1 << CAUSEB_CE));

        return EMULATE_DONE;
}

enum emulation_result kvm_mips_emulate_ri_exc(u32 cause,
                                              u32 *opc,
                                              struct kvm_run *run,
                                              struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        enum emulation_result er = EMULATE_DONE;

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("Delivering RI @ pc %#lx\n", arch->pc);

                kvm_change_c0_guest_cause(cop0, (0xff),
                                          (EXCCODE_RI << CAUSEB_EXCCODE));

                /* Set PC to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x180;

        } else {
                kvm_err("Trying to deliver RI when EXL is already set\n");
                er = EMULATE_FAIL;
        }

        return er;
}

enum emulation_result kvm_mips_emulate_bp_exc(u32 cause,
                                              u32 *opc,
                                              struct kvm_run *run,
                                              struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        enum emulation_result er = EMULATE_DONE;

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("Delivering BP @ pc %#lx\n", arch->pc);

                kvm_change_c0_guest_cause(cop0, (0xff),
                                          (EXCCODE_BP << CAUSEB_EXCCODE));

                /* Set PC to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x180;

        } else {
                kvm_err("Trying to deliver BP when EXL is already set\n");
                er = EMULATE_FAIL;
        }

        return er;
}

enum emulation_result kvm_mips_emulate_trap_exc(u32 cause,
                                                u32 *opc,
                                                struct kvm_run *run,
                                                struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        enum emulation_result er = EMULATE_DONE;

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("Delivering TRAP @ pc %#lx\n", arch->pc);

                kvm_change_c0_guest_cause(cop0, (0xff),
                                          (EXCCODE_TR << CAUSEB_EXCCODE));

                /* Set PC to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x180;

        } else {
                kvm_err("Trying to deliver TRAP when EXL is already set\n");
                er = EMULATE_FAIL;
        }

        return er;
}

enum emulation_result kvm_mips_emulate_msafpe_exc(u32 cause,
                                                  u32 *opc,
                                                  struct kvm_run *run,
                                                  struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        enum emulation_result er = EMULATE_DONE;

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("Delivering MSAFPE @ pc %#lx\n", arch->pc);

                kvm_change_c0_guest_cause(cop0, (0xff),
                                          (EXCCODE_MSAFPE << CAUSEB_EXCCODE));

                /* Set PC to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x180;

        } else {
                kvm_err("Trying to deliver MSAFPE when EXL is already set\n");
                er = EMULATE_FAIL;
        }

        return er;
}

enum emulation_result kvm_mips_emulate_fpe_exc(u32 cause,
                                               u32 *opc,
                                               struct kvm_run *run,
                                               struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        enum emulation_result er = EMULATE_DONE;

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("Delivering FPE @ pc %#lx\n", arch->pc);

                kvm_change_c0_guest_cause(cop0, (0xff),
                                          (EXCCODE_FPE << CAUSEB_EXCCODE));

                /* Set PC to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x180;

        } else {
                kvm_err("Trying to deliver FPE when EXL is already set\n");
                er = EMULATE_FAIL;
        }

        return er;
}

enum emulation_result kvm_mips_emulate_msadis_exc(u32 cause,
                                                  u32 *opc,
                                                  struct kvm_run *run,
                                                  struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        enum emulation_result er = EMULATE_DONE;

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_debug("Delivering MSADIS @ pc %#lx\n", arch->pc);

                kvm_change_c0_guest_cause(cop0, (0xff),
                                          (EXCCODE_MSADIS << CAUSEB_EXCCODE));

                /* Set PC to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x180;

        } else {
                kvm_err("Trying to deliver MSADIS when EXL is already set\n");
                er = EMULATE_FAIL;
        }

        return er;
}

enum emulation_result kvm_mips_handle_ri(u32 cause, u32 *opc,
                                         struct kvm_run *run,
                                         struct kvm_vcpu *vcpu)
{
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        enum emulation_result er = EMULATE_DONE;
        unsigned long curr_pc;
        union mips_instruction inst;

        /*
         * Update PC and hold onto current PC in case there is
         * an error and we want to rollback the PC
         */
        curr_pc = vcpu->arch.pc;
        er = update_pc(vcpu, cause);
        if (er == EMULATE_FAIL)
                return er;

        /* Fetch the instruction. */
        if (cause & CAUSEF_BD)
                opc += 1;

        inst.word = kvm_get_inst(opc, vcpu);

        if (inst.word == KVM_INVALID_INST) {
                kvm_err("%s: Cannot get inst @ %p\n", __func__, opc);
                return EMULATE_FAIL;
        }

        if (inst.r_format.opcode == spec3_op &&
            inst.r_format.func == rdhwr_op &&
            inst.r_format.rs == 0 &&
            (inst.r_format.re >> 3) == 0) {
                int usermode = !KVM_GUEST_KERNEL_MODE(vcpu);
                int rd = inst.r_format.rd;
                int rt = inst.r_format.rt;
                int sel = inst.r_format.re & 0x7;

                /* If usermode, check RDHWR rd is allowed by guest HWREna */
                if (usermode && !(kvm_read_c0_guest_hwrena(cop0) & BIT(rd))) {
                        kvm_debug("RDHWR %#x disallowed by HWREna @ %p\n",
                                  rd, opc);
                        goto emulate_ri;
                }
                switch (rd) {
                case MIPS_HWR_CPUNUM:           /* CPU number */
                        arch->gprs[rt] = vcpu->vcpu_id;
                        break;
                case MIPS_HWR_SYNCISTEP:        /* SYNCI length */
                        arch->gprs[rt] = min(current_cpu_data.dcache.linesz,
                                             current_cpu_data.icache.linesz);
                        break;
                case MIPS_HWR_CC:               /* Read count register */
                        arch->gprs[rt] = (s32)kvm_mips_read_count(vcpu);
                        break;
                case MIPS_HWR_CCRES:            /* Count register resolution */
                        switch (current_cpu_data.cputype) {
                        case CPU_20KC:
                        case CPU_25KF:
                                arch->gprs[rt] = 1;
                                break;
                        default:
                                arch->gprs[rt] = 2;
                        }
                        break;
                case MIPS_HWR_ULR:              /* Read UserLocal register */
                        arch->gprs[rt] = kvm_read_c0_guest_userlocal(cop0);
                        break;

                default:
                        kvm_debug("RDHWR %#x not supported @ %p\n", rd, opc);
                        goto emulate_ri;
                }

                trace_kvm_hwr(vcpu, KVM_TRACE_RDHWR, KVM_TRACE_HWR(rd, sel),
                              vcpu->arch.gprs[rt]);
        } else {
                kvm_debug("Emulate RI not supported @ %p: %#x\n",
                          opc, inst.word);
                goto emulate_ri;
        }

        return EMULATE_DONE;

emulate_ri:
        /*
         * Rollback PC (if in branch delay slot then the PC already points to
         * branch target), and pass the RI exception to the guest OS.
         */
        vcpu->arch.pc = curr_pc;
        return kvm_mips_emulate_ri_exc(cause, opc, run, vcpu);
}

enum emulation_result kvm_mips_complete_mmio_load(struct kvm_vcpu *vcpu,
                                                  struct kvm_run *run)
{
        unsigned long *gpr = &vcpu->arch.gprs[vcpu->arch.io_gpr];
        enum emulation_result er = EMULATE_DONE;

        if (run->mmio.len > sizeof(*gpr)) {
                kvm_err("Bad MMIO length: %d", run->mmio.len);
                er = EMULATE_FAIL;
                goto done;
        }

        er = update_pc(vcpu, vcpu->arch.pending_load_cause);
        if (er == EMULATE_FAIL)
                return er;

        switch (run->mmio.len) {
        case 4:
                *gpr = *(s32 *) run->mmio.data;
                break;

        case 2:
                if (vcpu->mmio_needed == 2)
                        *gpr = *(s16 *) run->mmio.data;
                else
                        *gpr = *(u16 *)run->mmio.data;

                break;
        case 1:
                if (vcpu->mmio_needed == 2)
                        *gpr = *(s8 *) run->mmio.data;
                else
                        *gpr = *(u8 *) run->mmio.data;
                break;
        }

        if (vcpu->arch.pending_load_cause & CAUSEF_BD)
                kvm_debug("[%#lx] Completing %d byte BD Load to gpr %d (0x%08lx) type %d\n",
                          vcpu->arch.pc, run->mmio.len, vcpu->arch.io_gpr, *gpr,
                          vcpu->mmio_needed);

done:
        return er;
}

static enum emulation_result kvm_mips_emulate_exc(u32 cause,
                                                  u32 *opc,
                                                  struct kvm_run *run,
                                                  struct kvm_vcpu *vcpu)
{
        u32 exccode = (cause >> CAUSEB_EXCCODE) & 0x1f;
        struct mips_coproc *cop0 = vcpu->arch.cop0;
        struct kvm_vcpu_arch *arch = &vcpu->arch;
        enum emulation_result er = EMULATE_DONE;

        if ((kvm_read_c0_guest_status(cop0) & ST0_EXL) == 0) {
                /* save old pc */
                kvm_write_c0_guest_epc(cop0, arch->pc);
                kvm_set_c0_guest_status(cop0, ST0_EXL);

                if (cause & CAUSEF_BD)
                        kvm_set_c0_guest_cause(cop0, CAUSEF_BD);
                else
                        kvm_clear_c0_guest_cause(cop0, CAUSEF_BD);

                kvm_change_c0_guest_cause(cop0, (0xff),
                                          (exccode << CAUSEB_EXCCODE));

                /* Set PC to the exception entry point */
                arch->pc = KVM_GUEST_KSEG0 + 0x180;
                kvm_write_c0_guest_badvaddr(cop0, vcpu->arch.host_cp0_badvaddr);

                kvm_debug("Delivering EXC %d @ pc %#lx, badVaddr: %#lx\n",
                          exccode, kvm_read_c0_guest_epc(cop0),
                          kvm_read_c0_guest_badvaddr(cop0));
        } else {
                kvm_err("Trying to deliver EXC when EXL is already set\n");
                er = EMULATE_FAIL;
        }

        return er;
}

enum emulation_result kvm_mips_check_privilege(u32 cause,
                                               u32 *opc,
                                               struct kvm_run *run,
                                               struct kvm_vcpu *vcpu)
{
        enum emulation_result er = EMULATE_DONE;
        u32 exccode = (cause >> CAUSEB_EXCCODE) & 0x1f;
        unsigned long badvaddr = vcpu->arch.host_cp0_badvaddr;

        int usermode = !KVM_GUEST_KERNEL_MODE(vcpu);

        if (usermode) {
                switch (exccode) {
                case EXCCODE_INT:
                case EXCCODE_SYS:
                case EXCCODE_BP:
                case EXCCODE_RI:
                case EXCCODE_TR:
                case EXCCODE_MSAFPE:
                case EXCCODE_FPE:
                case EXCCODE_MSADIS:
                        break;

                case EXCCODE_CPU:
                        if (((cause & CAUSEF_CE) >> CAUSEB_CE) == 0)
                                er = EMULATE_PRIV_FAIL;
                        break;

                case EXCCODE_MOD:
                        break;

                case EXCCODE_TLBL:
                        /*
                         * We we are accessing Guest kernel space, then send an
                         * address error exception to the guest
                         */
                        if (badvaddr >= (unsigned long) KVM_GUEST_KSEG0) {
                                kvm_debug("%s: LD MISS @ %#lx\n", __func__,
                                          badvaddr);
                                cause &= ~0xff;
                                cause |= (EXCCODE_ADEL << CAUSEB_EXCCODE);
                                er = EMULATE_PRIV_FAIL;
                        }
                        break;

                case EXCCODE_TLBS:
                        /*
                         * We we are accessing Guest kernel space, then send an
                         * address error exception to the guest
                         */
                        if (badvaddr >= (unsigned long) KVM_GUEST_KSEG0) {
                                kvm_debug("%s: ST MISS @ %#lx\n", __func__,
                                          badvaddr);
                                cause &= ~0xff;
                                cause |= (EXCCODE_ADES << CAUSEB_EXCCODE);
                                er = EMULATE_PRIV_FAIL;
                        }
                        break;

                case EXCCODE_ADES:
                        kvm_debug("%s: address error ST @ %#lx\n", __func__,
                                  badvaddr);
                        if ((badvaddr & PAGE_MASK) == KVM_GUEST_COMMPAGE_ADDR) {
                                cause &= ~0xff;
                                cause |= (EXCCODE_TLBS << CAUSEB_EXCCODE);
                        }
                        er = EMULATE_PRIV_FAIL;
                        break;
                case EXCCODE_ADEL:
                        kvm_debug("%s: address error LD @ %#lx\n", __func__,
                                  badvaddr);
                        if ((badvaddr & PAGE_MASK) == KVM_GUEST_COMMPAGE_ADDR) {
                                cause &= ~0xff;
                                cause |= (EXCCODE_TLBL << CAUSEB_EXCCODE);
                        }
                        er = EMULATE_PRIV_FAIL;
                        break;
                default:
                        er = EMULATE_PRIV_FAIL;
                        break;
                }
        }

        if (er == EMULATE_PRIV_FAIL)
                kvm_mips_emulate_exc(cause, opc, run, vcpu);

        return er;
}

/*
 * User Address (UA) fault, this could happen if
 * (1) TLB entry not present/valid in both Guest and shadow host TLBs, in this
 *     case we pass on the fault to the guest kernel and let it handle it.
 * (2) TLB entry is present in the Guest TLB but not in the shadow, in this
 *     case we inject the TLB from the Guest TLB into the shadow host TLB
 */
enum emulation_result kvm_mips_handle_tlbmiss(u32 cause,
                                              u32 *opc,
                                              struct kvm_run *run,
                                              struct kvm_vcpu *vcpu)
{
        enum emulation_result er = EMULATE_DONE;
        u32 exccode = (cause >> CAUSEB_EXCCODE) & 0x1f;
        unsigned long va = vcpu->arch.host_cp0_badvaddr;
        int index;

        kvm_debug("kvm_mips_handle_tlbmiss: badvaddr: %#lx\n",
                  vcpu->arch.host_cp0_badvaddr);

        /*
         * KVM would not have got the exception if this entry was valid in the
         * shadow host TLB. Check the Guest TLB, if the entry is not there then
         * send the guest an exception. The guest exc handler should then inject
         * an entry into the guest TLB.
         */
        index = kvm_mips_guest_tlb_lookup(vcpu,
                      (va & VPN2_MASK) |
                      (kvm_read_c0_guest_entryhi(vcpu->arch.cop0) &
                       KVM_ENTRYHI_ASID));
        if (index < 0) {
                if (exccode == EXCCODE_TLBL) {
                        er = kvm_mips_emulate_tlbmiss_ld(cause, opc, run, vcpu);
                } else if (exccode == EXCCODE_TLBS) {
                        er = kvm_mips_emulate_tlbmiss_st(cause, opc, run, vcpu);
                } else {
                        kvm_err("%s: invalid exc code: %d\n", __func__,
                                exccode);
                        er = EMULATE_FAIL;
                }
        } else {
                struct kvm_mips_tlb *tlb = &vcpu->arch.guest_tlb[index];

                /*
                 * Check if the entry is valid, if not then setup a TLB invalid
                 * exception to the guest
                 */
                if (!TLB_IS_VALID(*tlb, va)) {
                        if (exccode == EXCCODE_TLBL) {
                                er = kvm_mips_emulate_tlbinv_ld(cause, opc, run,
                                                                vcpu);
                        } else if (exccode == EXCCODE_TLBS) {
                                er = kvm_mips_emulate_tlbinv_st(cause, opc, run,
                                                                vcpu);
                        } else {
                                kvm_err("%s: invalid exc code: %d\n", __func__,
                                        exccode);
                                er = EMULATE_FAIL;
                        }
                } else {
                        kvm_debug("Injecting hi: %#lx, lo0: %#lx, lo1: %#lx into shadow host TLB\n",
                                  tlb->tlb_hi, tlb->tlb_lo[0], tlb->tlb_lo[1]);
                        /*
                         * OK we have a Guest TLB entry, now inject it into the
                         * shadow host TLB
                         */
                        if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb)) {
                                kvm_err("%s: handling mapped seg tlb fault for %lx, index: %u, vcpu: %p, ASID: %#lx\n",
                                        __func__, va, index, vcpu,
                                        read_c0_entryhi());
                                er = EMULATE_FAIL;
                        }
                }
        }

        return er;
}