/*
 * Copyright 2012 Michael Ellerman, IBM Corporation.
 * Copyright 2012 Benjamin Herrenschmidt, IBM Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/kvm_host.h>
#include <linux/err.h>

#include <asm/kvm_book3s.h>
#include <asm/kvm_ppc.h>
#include <asm/hvcall.h>
#include <asm/xics.h>
#include <asm/debug.h>
#include <asm/synch.h>
#include <asm/ppc-opcode.h>

#include "book3s_xics.h"

#define DEBUG_PASSUP

static inline void rm_writeb(unsigned long paddr, u8 val)
{
        __asm__ __volatile__("sync; stbcix %0,0,%1"
                : : "r" (val), "r" (paddr) : "memory");
}

static void icp_rm_set_vcpu_irq(struct kvm_vcpu *vcpu,
                                struct kvm_vcpu *this_vcpu)
{
        struct kvmppc_icp *this_icp = this_vcpu->arch.icp;
        unsigned long xics_phys;
        int cpu;

        /* Mark the target VCPU as having an interrupt pending */
        vcpu->stat.queue_intr++;
        set_bit(BOOK3S_IRQPRIO_EXTERNAL_LEVEL, &vcpu->arch.pending_exceptions);

        /* Kick self ? Just set MER and return */
        if (vcpu == this_vcpu) {
                mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) | LPCR_MER);
                return;
        }

        /* Check if the core is loaded, if not, too hard */
        cpu = vcpu->cpu;
        if (cpu < 0 || cpu >= nr_cpu_ids) {
                this_icp->rm_action |= XICS_RM_KICK_VCPU;
                this_icp->rm_kick_target = vcpu;
                return;
        }
        /* In SMT cpu will always point to thread 0, we adjust it */
        cpu += vcpu->arch.ptid;

        /* Not too hard, then poke the target */
        xics_phys = paca[cpu].kvm_hstate.xics_phys;
        rm_writeb(xics_phys + XICS_MFRR, IPI_PRIORITY);
}

static void icp_rm_clr_vcpu_irq(struct kvm_vcpu *vcpu)
{
        /* Note: Only called on self ! */
        clear_bit(BOOK3S_IRQPRIO_EXTERNAL_LEVEL,
                  &vcpu->arch.pending_exceptions);
        mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~LPCR_MER);
}

static inline bool icp_rm_try_update(struct kvmppc_icp *icp,
                                     union kvmppc_icp_state old,
                                     union kvmppc_icp_state new)
{
        struct kvm_vcpu *this_vcpu = local_paca->kvm_hstate.kvm_vcpu;
        bool success;

        /* Calculate new output value */
        new.out_ee = (new.xisr && (new.pending_pri < new.cppr));

        /* Attempt atomic update */
        success = cmpxchg64(&icp->state.raw, old.raw, new.raw) == old.raw;
        if (!success)
                goto bail;

        /*
         * Check for output state update
         *
         * Note that this is racy since another processor could be updating
         * the state already. This is why we never clear the interrupt output
         * here, we only ever set it. The clear only happens prior to doing
         * an update and only by the processor itself. Currently we do it
         * in Accept (H_XIRR) and Up_Cppr (H_XPPR).
         *
         * We also do not try to figure out whether the EE state has changed,
         * we unconditionally set it if the new state calls for it. The reason
         * for that is that we opportunistically remove the pending interrupt
         * flag when raising CPPR, so we need to set it back here if an
         * interrupt is still pending.
         */
        if (new.out_ee)
                icp_rm_set_vcpu_irq(icp->vcpu, this_vcpu);

        /* Expose the state change for debug purposes */
        this_vcpu->arch.icp->rm_dbgstate = new;
        this_vcpu->arch.icp->rm_dbgtgt = icp->vcpu;

 bail:
        return success;
}

static inline int check_too_hard(struct kvmppc_xics *xics,
                                 struct kvmppc_icp *icp)
{
        return (xics->real_mode_dbg || icp->rm_action) ? H_TOO_HARD : H_SUCCESS;
}

static void icp_rm_down_cppr(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
                             u8 new_cppr)
{
        union kvmppc_icp_state old_state, new_state;
        bool resend;

        /*
         * This handles several related states in one operation:
         *
         * ICP State: Down_CPPR
         *
         * Load CPPR with new value and if the XISR is 0
         * then check for resends:
         *
         * ICP State: Resend
         *
         * If MFRR is more favored than CPPR, check for IPIs
         * and notify ICS of a potential resend. This is done
         * asynchronously (when used in real mode, we will have
         * to exit here).
         *
         * We do not handle the complete Check_IPI as documented
         * here. In the PAPR, this state will be used for both
         * Set_MFRR and Down_CPPR. However, we know that we aren't
         * changing the MFRR state here so we don't need to handle
         * the case of an MFRR causing a reject of a pending irq,
         * this will have been handled when the MFRR was set in the
         * first place.
         *
         * Thus we don't have to handle rejects, only resends.
         *
         * When implementing real mode for HV KVM, resend will lead to
         * a H_TOO_HARD return and the whole transaction will be handled
         * in virtual mode.
         */
        do {
                old_state = new_state = ACCESS_ONCE(icp->state);

                /* Down_CPPR */
                new_state.cppr = new_cppr;

                /*
                 * Cut down Resend / Check_IPI / IPI
                 *
                 * The logic is that we cannot have a pending interrupt
                 * trumped by an IPI at this point (see above), so we
                 * know that either the pending interrupt is already an
                 * IPI (in which case we don't care to override it) or
                 * it's either more favored than us or non existent
                 */
                if (new_state.mfrr < new_cppr &&
                    new_state.mfrr <= new_state.pending_pri) {
                        new_state.pending_pri = new_state.mfrr;
                        new_state.xisr = XICS_IPI;
                }

                /* Latch/clear resend bit */
                resend = new_state.need_resend;
                new_state.need_resend = 0;

        } while (!icp_rm_try_update(icp, old_state, new_state));

        /*
         * Now handle resend checks. Those are asynchronous to the ICP
         * state update in HW (ie bus transactions) so we can handle them
         * separately here as well.
         */
        if (resend)
                icp->rm_action |= XICS_RM_CHECK_RESEND;
}


unsigned long kvmppc_rm_h_xirr(struct kvm_vcpu *vcpu)
{
        union kvmppc_icp_state old_state, new_state;
        struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
        struct kvmppc_icp *icp = vcpu->arch.icp;
        u32 xirr;

        if (!xics || !xics->real_mode)
                return H_TOO_HARD;

        /* First clear the interrupt */
        icp_rm_clr_vcpu_irq(icp->vcpu);

        /*
         * ICP State: Accept_Interrupt
         *
         * Return the pending interrupt (if any) along with the
         * current CPPR, then clear the XISR & set CPPR to the
         * pending priority
         */
        do {
                old_state = new_state = ACCESS_ONCE(icp->state);

                xirr = old_state.xisr | (((u32)old_state.cppr) << 24);
                if (!old_state.xisr)
                        break;
                new_state.cppr = new_state.pending_pri;
                new_state.pending_pri = 0xff;
                new_state.xisr = 0;

        } while (!icp_rm_try_update(icp, old_state, new_state));

        /* Return the result in GPR4 */
        vcpu->arch.gpr[4] = xirr;

        return check_too_hard(xics, icp);
}

int kvmppc_rm_h_ipi(struct kvm_vcpu *vcpu, unsigned long server,
                    unsigned long mfrr)
{
        union kvmppc_icp_state old_state, new_state;
        struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
        struct kvmppc_icp *icp, *this_icp = vcpu->arch.icp;
        u32 reject;
        bool resend;
        bool local;

        if (!xics || !xics->real_mode)
                return H_TOO_HARD;

        local = this_icp->server_num == server;
        if (local)
                icp = this_icp;
        else
                icp = kvmppc_xics_find_server(vcpu->kvm, server);
        if (!icp)
                return H_PARAMETER;

        /*
         * ICP state: Set_MFRR
         *
         * If the CPPR is more favored than the new MFRR, then
         * nothing needs to be done as there can be no XISR to
         * reject.
         *
         * If the CPPR is less favored, then we might be replacing
         * an interrupt, and thus need to possibly reject it as in
         *
         * ICP state: Check_IPI
         */
        do {
                old_state = new_state = ACCESS_ONCE(icp->state);

                /* Set_MFRR */
                new_state.mfrr = mfrr;

                /* Check_IPI */
                reject = 0;
                resend = false;
                if (mfrr < new_state.cppr) {
                        /* Reject a pending interrupt if not an IPI */
                        if (mfrr <= new_state.pending_pri)
                                reject = new_state.xisr;
                        new_state.pending_pri = mfrr;
                        new_state.xisr = XICS_IPI;
                }

                if (mfrr > old_state.mfrr && mfrr > new_state.cppr) {
                        resend = new_state.need_resend;
                        new_state.need_resend = 0;
                }
        } while (!icp_rm_try_update(icp, old_state, new_state));

        /* Pass rejects to virtual mode */
        if (reject && reject != XICS_IPI) {
                this_icp->rm_action |= XICS_RM_REJECT;
                this_icp->rm_reject = reject;
        }

        /* Pass resends to virtual mode */
        if (resend)
                this_icp->rm_action |= XICS_RM_CHECK_RESEND;

        return check_too_hard(xics, this_icp);
}

int kvmppc_rm_h_cppr(struct kvm_vcpu *vcpu, unsigned long cppr)
{
        union kvmppc_icp_state old_state, new_state;
        struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
        struct kvmppc_icp *icp = vcpu->arch.icp;
        u32 reject;

        if (!xics || !xics->real_mode)
                return H_TOO_HARD;

        /*
         * ICP State: Set_CPPR
         *
         * We can safely compare the new value with the current
         * value outside of the transaction as the CPPR is only
         * ever changed by the processor on itself
         */
        if (cppr > icp->state.cppr) {
                icp_rm_down_cppr(xics, icp, cppr);
                goto bail;
        } else if (cppr == icp->state.cppr)
                return H_SUCCESS;

        /*
         * ICP State: Up_CPPR
         *
         * The processor is raising its priority, this can result
         * in a rejection of a pending interrupt:
         *
         * ICP State: Reject_Current
         *
         * We can remove EE from the current processor, the update
         * transaction will set it again if needed
         */
        icp_rm_clr_vcpu_irq(icp->vcpu);

        do {
                old_state = new_state = ACCESS_ONCE(icp->state);

                reject = 0;
                new_state.cppr = cppr;

                if (cppr <= new_state.pending_pri) {
                        reject = new_state.xisr;
                        new_state.xisr = 0;
                        new_state.pending_pri = 0xff;
                }

        } while (!icp_rm_try_update(icp, old_state, new_state));

        /* Pass rejects to virtual mode */
        if (reject && reject != XICS_IPI) {
                icp->rm_action |= XICS_RM_REJECT;
                icp->rm_reject = reject;
        }
 bail:
        return check_too_hard(xics, icp);
}

int kvmppc_rm_h_eoi(struct kvm_vcpu *vcpu, unsigned long xirr)
{
        struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
        struct kvmppc_icp *icp = vcpu->arch.icp;
        struct kvmppc_ics *ics;
        struct ics_irq_state *state;
        u32 irq = xirr & 0x00ffffff;
        u16 src;

        if (!xics || !xics->real_mode)
                return H_TOO_HARD;

        /*
         * ICP State: EOI
         *
         * Note: If EOI is incorrectly used by SW to lower the CPPR
         * value (ie more favored), we do not check for rejection of
         * a pending interrupt, this is a SW error and PAPR sepcifies
         * that we don't have to deal with it.
         *
         * The sending of an EOI to the ICS is handled after the
         * CPPR update
         *
         * ICP State: Down_CPPR which we handle
         * in a separate function as it's shared with H_CPPR.
         */
        icp_rm_down_cppr(xics, icp, xirr >> 24);

        /* IPIs have no EOI */
        if (irq == XICS_IPI)
                goto bail;
        /*
         * EOI handling: If the interrupt is still asserted, we need to
         * resend it. We can take a lockless "peek" at the ICS state here.
         *
         * "Message" interrupts will never have "asserted" set
         */
        ics = kvmppc_xics_find_ics(xics, irq, &src);
        if (!ics)
                goto bail;
        state = &ics->irq_state[src];

        /* Still asserted, resend it, we make it look like a reject */
        if (state->asserted) {
                icp->rm_action |= XICS_RM_REJECT;
                icp->rm_reject = irq;
        }
 bail:
        return check_too_hard(xics, icp);
}