/*
 * 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/vmalloc.h>
#include <linux/fs.h>
#include <linux/memblock.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 "trace.h"

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

        if (epc & 3) {
                kvm_err("%s: unaligned epc\n", __func__);
                return -EINVAL;
        }

        /* Read the instruction */
        err = kvm_get_badinstrp((u32 *)epc, vcpu, &insn.word);
        if (err)
                return err;

        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;
                        fallthrough;
                case jr_op:
                        nextpc = arch->gprs[insn.r_format.rs];
                        break;
                default:
                        return -EINVAL;
                }
                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) {
                                kvm_err("%s: DSP branch but not DSP ASE\n",
                                        __func__);
                                return -EINVAL;
                        }

                        dspcontrol = rddsp(0x01);

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

                /* These are unconditional and in j_format. */
        case jal_op:
                arch->gprs[31] = instpc + 8;
                fallthrough;
        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__);
                return -EINVAL;

#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;
                return -EINVAL;
        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;
                return -EINVAL;
        case pop66_op:
        case pop76_op:
                /* only rs == 0 isn't compact branch */
                if (insn.i_format.rs != 0)
                        goto compact_branch;
                return -EINVAL;
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:
                /* Fall through - Compact branches not supported before R6 */
#endif
        default:
                return -EINVAL;
        }

        *out = nextpc;
        return 0;
}

enum emulation_result update_pc(struct kvm_vcpu *vcpu, u32 cause)
{
        int err;

        if (cause & CAUSEF_BD) {
                err = kvm_compute_return_epc(vcpu, vcpu->arch.pc,
                                             &vcpu->arch.pc);
                if (err)
                        return EMULATE_FAIL;
        } else {
                vcpu->arch.pc += 4;
        }

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

        return EMULATE_DONE;
}

/**
 * kvm_get_badinstr() - Get bad instruction encoding.
 * @opc:        Guest pointer to faulting instruction.
 * @vcpu:       KVM VCPU information.
 *
 * Gets the instruction encoding of the faulting instruction, using the saved
 * BadInstr register value if it exists, otherwise falling back to reading guest
 * memory at @opc.
 *
 * Returns:     The instruction encoding of the faulting instruction.
 */
int kvm_get_badinstr(u32 *opc, struct kvm_vcpu *vcpu, u32 *out)
{
        if (cpu_has_badinstr) {
                *out = vcpu->arch.host_cp0_badinstr;
                return 0;
        } else {
                WARN_ONCE(1, "CPU doesn't have BadInstr register\n");
                return -EINVAL;
        }
}

/**
 * kvm_get_badinstrp() - Get bad prior instruction encoding.
 * @opc:        Guest pointer to prior faulting instruction.
 * @vcpu:       KVM VCPU information.
 *
 * Gets the instruction encoding of the prior faulting instruction (the branch
 * containing the delay slot which faulted), using the saved BadInstrP register
 * value if it exists, otherwise falling back to reading guest memory at @opc.
 *
 * Returns:     The instruction encoding of the prior faulting instruction.
 */
int kvm_get_badinstrp(u32 *opc, struct kvm_vcpu *vcpu, u32 *out)
{
        if (cpu_has_badinstrp) {
                *out = vcpu->arch.host_cp0_badinstrp;
                return 0;
        } else {
                WARN_ONCE(1, "CPU doesn't have BadInstrp register\n");
                return -EINVAL;
        }
}

/**
 * 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).
 */
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.
 */
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_restore_hrtimer() - Restore hrtimer after a gap, updating expiry.
 * @vcpu:       Virtual CPU.
 * @before:     Time before Count was saved, lower bound of drift calculation.
 * @count:      CP0_Count at point of restore.
 * @min_drift:  Minimum amount of drift permitted before correction.
 *              Must be <= 0.
 *
 * Restores the timer from a particular @count, accounting for drift. This can
 * be used in conjunction with kvm_mips_freeze_timer() when a hardware timer is
 * to be used for a period of time, but the exact ktime corresponding to the
 * final Count that must be restored is not known.
 *
 * It is gauranteed that a timer interrupt immediately after restore will be
 * handled, but not if CP0_Compare is exactly at @count. That case should
 * already be handled when the hardware timer state is saved.
 *
 * Assumes !kvm_mips_count_disabled(@vcpu) (guest CP0_Count timer is not
 * stopped).
 *
 * Returns:     Amount of correction to count_bias due to drift.
 */
int kvm_mips_restore_hrtimer(struct kvm_vcpu *vcpu, ktime_t before,
                             u32 count, int min_drift)
{
        ktime_t now, count_time;
        u32 now_count, before_count;
        u64 delta;
        int drift, ret = 0;

        /* Calculate expected count at before */
        before_count = vcpu->arch.count_bias +
                        kvm_mips_ktime_to_count(vcpu, before);

        /*
         * Detect significantly negative drift, where count is lower than
         * expected. Some negative drift is expected when hardware counter is
         * set after kvm_mips_freeze_timer(), and it is harmless to allow the
         * time to jump forwards a little, within reason. If the drift is too
         * significant, adjust the bias to avoid a big Guest.CP0_Count jump.
         */
        drift = count - before_count;
        if (drift < min_drift) {
                count_time = before;
                vcpu->arch.count_bias += drift;
                ret = drift;
                goto resume;
        }

        /* Calculate expected count right now */
        now = ktime_get();
        now_count = vcpu->arch.count_bias + kvm_mips_ktime_to_count(vcpu, now);

        /*
         * Detect positive drift, where count is higher than expected, and
         * adjust the bias to avoid guest time going backwards.
         */
        drift = count - now_count;
        if (drift > 0) {
                count_time = now;
                vcpu->arch.count_bias += drift;
                ret = drift;
                goto resume;
        }

        /* Subtract nanosecond delta to find ktime when count was read */
        delta = (u64)(u32)(now_count - count);
        delta = div_u64(delta * NSEC_PER_SEC, vcpu->arch.count_hz);
        count_time = ktime_sub_ns(now, delta);

resume:
        /* Resume using the calculated ktime */
        kvm_mips_resume_hrtimer(vcpu, count_time, count);
        return ret;
}

/**
 * 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.
 * @count_hz:   Frequency of timer.
 *
 * Initialise the timer to the specified frequency, zero it, and set it going if
 * it's enabled.
 */
void kvm_mips_init_count(struct kvm_vcpu *vcpu, unsigned long count_hz)
{
        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;

        /* 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);
        s32 delta = compare - old_compare;
        u32 cause;
        ktime_t now = ktime_set(0, 0); /* silence bogus GCC warning */
        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;
        }

        /*
         * If guest CP0_Compare moves forward, CP0_GTOffset should be adjusted
         * too to prevent guest CP0_Count hitting guest CP0_Compare.
         *
         * The new GTOffset corresponds to the new value of CP0_Compare, and is
         * set prior to it being written into the guest context. We disable
         * preemption until the new value is written to prevent restore of a
         * GTOffset corresponding to the old CP0_Compare value.
         */
        if (delta > 0) {
                preempt_disable();
                write_c0_gtoffset(compare - read_c0_count());
                back_to_back_c0_hazard();
        }

        /* 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);
        else
                /*
                 * With VZ, writing CP0_Compare acks (clears) CP0_Cause.TI, so
                 * preserve guest CP0_Cause.TI if we don't want to ack it.
                 */
                cause = kvm_read_c0_guest_cause(cop0);

        kvm_write_c0_guest_compare(cop0, compare);

        if (delta > 0)
                preempt_enable();

        back_to_back_c0_hazard();

        if (!ack && cause & CAUSEF_TI)
                kvm_write_c0_guest_cause(cop0, cause);

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

        /*
         * If guest CP0_Compare is moving backward, we delay CP0_GTOffset change
         * until after the new CP0_Compare is written, otherwise new guest
         * CP0_Count could hit new guest CP0_Compare.
         */
        if (delta <= 0)
                write_c0_gtoffset(compare - read_c0_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_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) {
                kvm_vz_lose_htimer(vcpu);
                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)) {
                        kvm_clear_request(KVM_REQ_UNHALT, vcpu);
                        vcpu->run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
                }
        }

        return EMULATE_DONE;
}

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

        run->mmio.phys_addr = kvm_mips_callbacks->gva_to_gpa(
                                                vcpu->arch.host_cp0_badvaddr);
        if (run->mmio.phys_addr == KVM_INVALID_ADDR)
                goto out_fail;

        switch (inst.i_format.opcode) {
#if defined(CONFIG_64BIT)
        case sd_op:

                run->mmio.len = 8;
                *(u64 *)data = vcpu->arch.gprs[rt];

                kvm_debug("[%#lx] OP_SD: eaddr: %#lx, gpr: %#lx, data: %#llx\n",
                          vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
                          vcpu->arch.gprs[rt], *(u64 *)data);
                break;
#endif

        case sw_op:
                run->mmio.len = 4;
                *(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:
                run->mmio.len = 2;
                *(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], *(u16 *)data);
                break;

        case sb_op:
                run->mmio.len = 1;
                *(u8 *)data = vcpu->arch.gprs[rt];

                kvm_debug("[%#lx] OP_SB: eaddr: %#lx, gpr: %#lx, data: %#x\n",
                          vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
                          vcpu->arch.gprs[rt], *(u8 *)data);
                break;

        case swl_op:
                run->mmio.phys_addr = kvm_mips_callbacks->gva_to_gpa(
                                        vcpu->arch.host_cp0_badvaddr) & (~0x3);
                run->mmio.len = 4;
                imme = vcpu->arch.host_cp0_badvaddr & 0x3;
                switch (imme) {
                case 0:
                        *(u32 *)data = ((*(u32 *)data) & 0xffffff00) |
                                        (vcpu->arch.gprs[rt] >> 24);
                        break;
                case 1:
                        *(u32 *)data = ((*(u32 *)data) & 0xffff0000) |
                                        (vcpu->arch.gprs[rt] >> 16);
                        break;
                case 2:
                        *(u32 *)data = ((*(u32 *)data) & 0xff000000) |
                                        (vcpu->arch.gprs[rt] >> 8);
                        break;
                case 3:
                        *(u32 *)data = vcpu->arch.gprs[rt];
                        break;
                default:
                        break;
                }

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

        case swr_op:
                run->mmio.phys_addr = kvm_mips_callbacks->gva_to_gpa(
                                        vcpu->arch.host_cp0_badvaddr) & (~0x3);
                run->mmio.len = 4;
                imme = vcpu->arch.host_cp0_badvaddr & 0x3;
                switch (imme) {
                case 0:
                        *(u32 *)data = vcpu->arch.gprs[rt];
                        break;
                case 1:
                        *(u32 *)data = ((*(u32 *)data) & 0xff) |
                                        (vcpu->arch.gprs[rt] << 8);
                        break;
                case 2:
                        *(u32 *)data = ((*(u32 *)data) & 0xffff) |
                                        (vcpu->arch.gprs[rt] << 16);
                        break;
                case 3:
                        *(u32 *)data = ((*(u32 *)data) & 0xffffff) |
                                        (vcpu->arch.gprs[rt] << 24);
                        break;
                default:
                        break;
                }

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

#if defined(CONFIG_64BIT)
        case sdl_op:
                run->mmio.phys_addr = kvm_mips_callbacks->gva_to_gpa(
                                        vcpu->arch.host_cp0_badvaddr) & (~0x7);

                run->mmio.len = 8;
                imme = vcpu->arch.host_cp0_badvaddr & 0x7;
                switch (imme) {
                case 0:
                        *(u64 *)data = ((*(u64 *)data) & 0xffffffffffffff00) |
                                        ((vcpu->arch.gprs[rt] >> 56) & 0xff);
                        break;
                case 1:
                        *(u64 *)data = ((*(u64 *)data) & 0xffffffffffff0000) |
                                        ((vcpu->arch.gprs[rt] >> 48) & 0xffff);
                        break;
                case 2:
                        *(u64 *)data = ((*(u64 *)data) & 0xffffffffff000000) |
                                        ((vcpu->arch.gprs[rt] >> 40) & 0xffffff);
                        break;
                case 3:
                        *(u64 *)data = ((*(u64 *)data) & 0xffffffff00000000) |
                                        ((vcpu->arch.gprs[rt] >> 32) & 0xffffffff);
                        break;
                case 4:
                        *(u64 *)data = ((*(u64 *)data) & 0xffffff0000000000) |
                                        ((vcpu->arch.gprs[rt] >> 24) & 0xffffffffff);
                        break;
                case 5:
                        *(u64 *)data = ((*(u64 *)data) & 0xffff000000000000) |
                                        ((vcpu->arch.gprs[rt] >> 16) & 0xffffffffffff);
                        break;
                case 6:
                        *(u64 *)data = ((*(u64 *)data) & 0xff00000000000000) |
                                        ((vcpu->arch.gprs[rt] >> 8) & 0xffffffffffffff);
                        break;
                case 7:
                        *(u64 *)data = vcpu->arch.gprs[rt];
                        break;
                default:
                        break;
                }

                kvm_debug("[%#lx] OP_SDL: eaddr: %#lx, gpr: %#lx, data: %llx\n",
                          vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
                          vcpu->arch.gprs[rt], *(u64 *)data);
                break;

        case sdr_op:
                run->mmio.phys_addr = kvm_mips_callbacks->gva_to_gpa(
                                        vcpu->arch.host_cp0_badvaddr) & (~0x7);

                run->mmio.len = 8;
                imme = vcpu->arch.host_cp0_badvaddr & 0x7;
                switch (imme) {
                case 0:
                        *(u64 *)data = vcpu->arch.gprs[rt];
                        break;
                case 1:
                        *(u64 *)data = ((*(u64 *)data) & 0xff) |
                                        (vcpu->arch.gprs[rt] << 8);
                        break;
                case 2:
                        *(u64 *)data = ((*(u64 *)data) & 0xffff) |
                                        (vcpu->arch.gprs[rt] << 16);
                        break;
                case 3:
                        *(u64 *)data = ((*(u64 *)data) & 0xffffff) |
                                        (vcpu->arch.gprs[rt] << 24);
                        break;
                case 4:
                        *(u64 *)data = ((*(u64 *)data) & 0xffffffff) |
                                        (vcpu->arch.gprs[rt] << 32);
                        break;
                case 5:
                        *(u64 *)data = ((*(u64 *)data) & 0xffffffffff) |
                                        (vcpu->arch.gprs[rt] << 40);
                        break;
                case 6:
                        *(u64 *)data = ((*(u64 *)data) & 0xffffffffffff) |
                                        (vcpu->arch.gprs[rt] << 48);
                        break;
                case 7:
                        *(u64 *)data = ((*(u64 *)data) & 0xffffffffffffff) |
                                        (vcpu->arch.gprs[rt] << 56);
                        break;
                default:
                        break;
                }

                kvm_debug("[%#lx] OP_SDR: eaddr: %#lx, gpr: %#lx, data: %llx\n",
                          vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
                          vcpu->arch.gprs[rt], *(u64 *)data);
                break;
#endif

#ifdef CONFIG_CPU_LOONGSON64
        case sdc2_op:
                rt = inst.loongson3_lsdc2_format.rt;
                switch (inst.loongson3_lsdc2_format.opcode1) {
                /*
                 * Loongson-3 overridden sdc2 instructions.
                 * opcode1              instruction
                 *   0x0          gssbx: store 1 bytes from GPR
                 *   0x1          gsshx: store 2 bytes from GPR
                 *   0x2          gsswx: store 4 bytes from GPR
                 *   0x3          gssdx: store 8 bytes from GPR
                 */
                case 0x0:
                        run->mmio.len = 1;
                        *(u8 *)data = vcpu->arch.gprs[rt];

                        kvm_debug("[%#lx] OP_GSSBX: eaddr: %#lx, gpr: %#lx, data: %#x\n",
                                  vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
                                  vcpu->arch.gprs[rt], *(u8 *)data);
                        break;
                case 0x1:
                        run->mmio.len = 2;
                        *(u16 *)data = vcpu->arch.gprs[rt];

                        kvm_debug("[%#lx] OP_GSSSHX: eaddr: %#lx, gpr: %#lx, data: %#x\n",
                                  vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
                                  vcpu->arch.gprs[rt], *(u16 *)data);
                        break;
                case 0x2:
                        run->mmio.len = 4;
                        *(u32 *)data = vcpu->arch.gprs[rt];

                        kvm_debug("[%#lx] OP_GSSWX: eaddr: %#lx, gpr: %#lx, data: %#x\n",
                                  vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
                                  vcpu->arch.gprs[rt], *(u32 *)data);
                        break;
                case 0x3:
                        run->mmio.len = 8;
                        *(u64 *)data = vcpu->arch.gprs[rt];

                        kvm_debug("[%#lx] OP_GSSDX: eaddr: %#lx, gpr: %#lx, data: %#llx\n",
                                  vcpu->arch.pc, vcpu->arch.host_cp0_badvaddr,
                                  vcpu->arch.gprs[rt], *(u64 *)data);
                        break;
                default:
                        kvm_err("Godson Extended GS-Store not yet supported (inst=0x%08x)\n",
                                inst.word);
                        break;
                }
                break;
#endif
        default:
                kvm_err("Store not yet supported (inst=0x%08x)\n",
                        inst.word);
                goto out_fail;
        }

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

        r = kvm_io_bus_write(vcpu, KVM_MMIO_BUS,
                        run->mmio.phys_addr, run->mmio.len, data);

        if (!r) {
                vcpu->mmio_needed = 0;
                return EMULATE_DONE;
        }

        return EMULATE_DO_MMIO;

out_fail:
        /* Rollback PC if emulation was unsuccessful */
        vcpu->arch.pc = curr_pc;
        return EMULATE_FAIL;
}

enum emulation_result kvm_mips_emulate_load(union mips_instruction inst,
                                            u32 cause, struct kvm_vcpu *vcpu)
{
        struct kvm_run *run = vcpu->run;
        int r;
        enum emulation_result er;
        unsigned long curr_pc;
        u32 op, rt;
        unsigned int imme;

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

        /*
         * Find the resume PC now while we have safe and easy access to the
         * prior branch instruction, and save it for
         * kvm_mips_complete_mmio_load() to restore later.
         */
        curr_pc = vcpu->arch.pc;
        er = update_pc(vcpu, cause);
        if (er == EMULATE_FAIL)
                return er;
        vcpu->arch.io_pc = vcpu->arch.pc;
        vcpu->arch.pc = curr_pc;

        vcpu->arch.io_gpr = rt;

        run->mmio.phys_addr = kvm_mips_callbacks->gva_to_gpa(
                                                vcpu->arch.host_cp0_badvaddr);
        if (run->mmio.phys_addr == KVM_INVALID_ADDR)
                return EMULATE_FAIL;

        vcpu->mmio_needed = 2;  /* signed */
        switch (op) {
#if defined(CONFIG_64BIT)
        case ld_op:
                run->mmio.len = 8;
                break;

        case lwu_op:
                vcpu->mmio_needed = 1;  /* unsigned */
                fallthrough;
#endif
        case lw_op:
                run->mmio.len = 4;
                break;

        case lhu_op:
                vcpu->mmio_needed = 1;  /* unsigned */
                fallthrough;
        case lh_op:
                run->mmio.len = 2;
                break;

        case lbu_op:
                vcpu->mmio_needed = 1;  /* unsigned */
                fallthrough;
        case lb_op:
                run->mmio.len = 1;
                break;

        case lwl_op:
                run->mmio.phys_addr = kvm_mips_callbacks->gva_to_gpa(
                                        vcpu->arch.host_cp0_badvaddr) & (~0x3);

                run->mmio.len = 4;
                imme = vcpu->arch.host_cp0_badvaddr & 0x3;
                switch (imme) {
                case 0:
                        vcpu->mmio_needed = 3;  /* 1 byte */
                        break;
                case 1:
                        vcpu->mmio_needed = 4;  /* 2 bytes */
                        break;
                case 2:
                        vcpu->mmio_needed = 5;  /* 3 bytes */
                        break;
                case 3:
                        vcpu->mmio_needed = 6;  /* 4 bytes */
                        break;
                default:
                        break;
                }
                break;

        case lwr_op:
                run->mmio.phys_addr = kvm_mips_callbacks->gva_to_gpa(
                                        vcpu->arch.host_cp0_badvaddr) & (~0x3);

                run->mmio.len = 4;
                imme = vcpu->arch.host_cp0_badvaddr & 0x3;
                switch (imme) {
                case 0:
                        vcpu->mmio_needed = 7;  /* 4 bytes */
                        break;
                case 1:
                        vcpu->mmio_needed = 8;  /* 3 bytes */
                        break;
                case 2:
                        vcpu->mmio_needed = 9;  /* 2 bytes */
                        break;
                case 3:
                        vcpu->mmio_needed = 10; /* 1 byte */
                        break;
                default:
                        break;
                }
                break;

#if defined(CONFIG_64BIT)
        case ldl_op:
                run->mmio.phys_addr = kvm_mips_callbacks->gva_to_gpa(
                                        vcpu->arch.host_cp0_badvaddr) & (~0x7);

                run->mmio.len = 8;
                imme = vcpu->arch.host_cp0_badvaddr & 0x7;
                switch (imme) {
                case 0:
                        vcpu->mmio_needed = 11; /* 1 byte */
                        break;
                case 1:
                        vcpu->mmio_needed = 12; /* 2 bytes */
                        break;
                case 2:
                        vcpu->mmio_needed = 13; /* 3 bytes */
                        break;
                case 3:
                        vcpu->mmio_needed = 14; /* 4 bytes */
                        break;
                case 4:
                        vcpu->mmio_needed = 15; /* 5 bytes */
                        break;
                case 5:
                        vcpu->mmio_needed = 16; /* 6 bytes */
                        break;
                case 6:
                        vcpu->mmio_needed = 17; /* 7 bytes */
                        break;
                case 7:
                        vcpu->mmio_needed = 18; /* 8 bytes */
                        break;
                default:
                        break;
                }
                break;

        case ldr_op:
                run->mmio.phys_addr = kvm_mips_callbacks->gva_to_gpa(
                                        vcpu->arch.host_cp0_badvaddr) & (~0x7);

                run->mmio.len = 8;
                imme = vcpu->arch.host_cp0_badvaddr & 0x7;
                switch (imme) {
                case 0:
                        vcpu->mmio_needed = 19; /* 8 bytes */
                        break;
                case 1:
                        vcpu->mmio_needed = 20; /* 7 bytes */
                        break;
                case 2:
                        vcpu->mmio_needed = 21; /* 6 bytes */
                        break;
                case 3:
                        vcpu->mmio_needed = 22; /* 5 bytes */
                        break;
                case 4:
                        vcpu->mmio_needed = 23; /* 4 bytes */
                        break;
                case 5:
                        vcpu->mmio_needed = 24; /* 3 bytes */
                        break;
                case 6:
                        vcpu->mmio_needed = 25; /* 2 bytes */
                        break;
                case 7:
                        vcpu->mmio_needed = 26; /* 1 byte */
                        break;
                default:
                        break;
                }
                break;
#endif

#ifdef CONFIG_CPU_LOONGSON64
        case ldc2_op:
                rt = inst.loongson3_lsdc2_format.rt;
                switch (inst.loongson3_lsdc2_format.opcode1) {
                /*
                 * Loongson-3 overridden ldc2 instructions.
                 * opcode1              instruction
                 *   0x0          gslbx: store 1 bytes from GPR
                 *   0x1          gslhx: store 2 bytes from GPR
                 *   0x2          gslwx: store 4 bytes from GPR
                 *   0x3          gsldx: store 8 bytes from GPR
                 */
                case 0x0:
                        run->mmio.len = 1;
                        vcpu->mmio_needed = 27; /* signed */
                        break;
                case 0x1:
                        run->mmio.len = 2;
                        vcpu->mmio_needed = 28; /* signed */
                        break;
                case 0x2:
                        run->mmio.len = 4;
                        vcpu->mmio_needed = 29; /* signed */
                        break;
                case 0x3:
                        run->mmio.len = 8;
                        vcpu->mmio_needed = 30; /* signed */
                        break;
                default:
                        kvm_err("Godson Extended GS-Load for float not yet supported (inst=0x%08x)\n",
                                inst.word);
                        break;
                }
                break;
#endif

        default:
                kvm_err("Load not yet supported (inst=0x%08x)\n",
                        inst.word);
                vcpu->mmio_needed = 0;
                return EMULATE_FAIL;
        }

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

        r = kvm_io_bus_read(vcpu, KVM_MMIO_BUS,
                        run->mmio.phys_addr, run->mmio.len, run->mmio.data);

        if (!r) {
                kvm_mips_complete_mmio_load(vcpu);
                vcpu->mmio_needed = 0;
                return EMULATE_DONE;
        }

        return EMULATE_DO_MMIO;
}

enum emulation_result kvm_mips_complete_mmio_load(struct kvm_vcpu *vcpu)
{
        struct kvm_run *run = vcpu->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;
        }

        /* Restore saved resume PC */
        vcpu->arch.pc = vcpu->arch.io_pc;

        switch (run->mmio.len) {
        case 8:
                switch (vcpu->mmio_needed) {
                case 11:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffffffffffff) |
                                (((*(s64 *)run->mmio.data) & 0xff) << 56);
                        break;
                case 12:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffffffffff) |
                                (((*(s64 *)run->mmio.data) & 0xffff) << 48);
                        break;
                case 13:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffffffff) |
                                (((*(s64 *)run->mmio.data) & 0xffffff) << 40);
                        break;
                case 14:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffffff) |
                                (((*(s64 *)run->mmio.data) & 0xffffffff) << 32);
                        break;
                case 15:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffff) |
                                (((*(s64 *)run->mmio.data) & 0xffffffffff) << 24);
                        break;
                case 16:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffff) |
                                (((*(s64 *)run->mmio.data) & 0xffffffffffff) << 16);
                        break;
                case 17:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xff) |
                                (((*(s64 *)run->mmio.data) & 0xffffffffffffff) << 8);
                        break;
                case 18:
                case 19:
                        *gpr = *(s64 *)run->mmio.data;
                        break;
                case 20:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xff00000000000000) |
                                ((((*(s64 *)run->mmio.data)) >> 8) & 0xffffffffffffff);
                        break;
                case 21:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffff000000000000) |
                                ((((*(s64 *)run->mmio.data)) >> 16) & 0xffffffffffff);
                        break;
                case 22:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffff0000000000) |
                                ((((*(s64 *)run->mmio.data)) >> 24) & 0xffffffffff);
                        break;
                case 23:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffffff00000000) |
                                ((((*(s64 *)run->mmio.data)) >> 32) & 0xffffffff);
                        break;
                case 24:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffffffff000000) |
                                ((((*(s64 *)run->mmio.data)) >> 40) & 0xffffff);
                        break;
                case 25:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffffffffff0000) |
                                ((((*(s64 *)run->mmio.data)) >> 48) & 0xffff);
                        break;
                case 26:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffffffffffff00) |
                                ((((*(s64 *)run->mmio.data)) >> 56) & 0xff);
                        break;
                default:
                        *gpr = *(s64 *)run->mmio.data;
                }
                break;

        case 4:
                switch (vcpu->mmio_needed) {
                case 1:
                        *gpr = *(u32 *)run->mmio.data;
                        break;
                case 2:
                        *gpr = *(s32 *)run->mmio.data;
                        break;
                case 3:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffff) |
                                (((*(s32 *)run->mmio.data) & 0xff) << 24);
                        break;
                case 4:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffff) |
                                (((*(s32 *)run->mmio.data) & 0xffff) << 16);
                        break;
                case 5:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xff) |
                                (((*(s32 *)run->mmio.data) & 0xffffff) << 8);
                        break;
                case 6:
                case 7:
                        *gpr = *(s32 *)run->mmio.data;
                        break;
                case 8:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xff000000) |
                                ((((*(s32 *)run->mmio.data)) >> 8) & 0xffffff);
                        break;
                case 9:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffff0000) |
                                ((((*(s32 *)run->mmio.data)) >> 16) & 0xffff);
                        break;
                case 10:
                        *gpr = (vcpu->arch.gprs[vcpu->arch.io_gpr] & 0xffffff00) |
                                ((((*(s32 *)run->mmio.data)) >> 24) & 0xff);
                        break;
                default:
                        *gpr = *(s32 *)run->mmio.data;
                }
                break;

        case 2:
                if (vcpu->mmio_needed == 1)
                        *gpr = *(u16 *)run->mmio.data;
                else
                        *gpr = *(s16 *)run->mmio.data;

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

done:
        return er;
}