// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2012 Michael Ellerman, IBM Corporation.
 * Copyright 2012 Benjamin Herrenschmidt, IBM Corporation
 */

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

#include <asm/kvm_book3s.h>
#include <asm/kvm_ppc.h>
#include <asm/hvcall.h>
#include <asm/xics.h>
#include <asm/synch.h>
#include <asm/cputhreads.h>
#include <asm/ppc-opcode.h>
#include <asm/pnv-pci.h>
#include <asm/opal.h>
#include <asm/smp.h>

#include "book3s_xics.h"

#define DEBUG_PASSUP

int h_ipi_redirect = 1;
EXPORT_SYMBOL(h_ipi_redirect);
int kvm_irq_bypass = 1;
EXPORT_SYMBOL(kvm_irq_bypass);

static void icp_rm_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
                            u32 new_irq, bool check_resend);
static int xics_opal_set_server(unsigned int hw_irq, int server_cpu);

/* -- ICS routines -- */
static void ics_rm_check_resend(struct kvmppc_xics *xics,
                                struct kvmppc_ics *ics, struct kvmppc_icp *icp)
{
        int i;

        for (i = 0; i < KVMPPC_XICS_IRQ_PER_ICS; i++) {
                struct ics_irq_state *state = &ics->irq_state[i];
                if (state->resend)
                        icp_rm_deliver_irq(xics, icp, state->number, true);
        }

}

/* -- ICP routines -- */

#ifdef CONFIG_SMP
static inline void icp_send_hcore_msg(int hcore, struct kvm_vcpu *vcpu)
{
        int hcpu;

        hcpu = hcore << threads_shift;
        kvmppc_host_rm_ops_hv->rm_core[hcore].rm_data = vcpu;
        smp_muxed_ipi_set_message(hcpu, PPC_MSG_RM_HOST_ACTION);
        kvmppc_set_host_ipi(hcpu);
        smp_mb();
        kvmhv_rm_send_ipi(hcpu);
}
#else
static inline void icp_send_hcore_msg(int hcore, struct kvm_vcpu *vcpu) { }
#endif

/*
 * We start the search from our current CPU Id in the core map
 * and go in a circle until we get back to our ID looking for a
 * core that is running in host context and that hasn't already
 * been targeted for another rm_host_ops.
 *
 * In the future, could consider using a fairer algorithm (one
 * that distributes the IPIs better)
 *
 * Returns -1, if no CPU could be found in the host
 * Else, returns a CPU Id which has been reserved for use
 */
static inline int grab_next_hostcore(int start,
                struct kvmppc_host_rm_core *rm_core, int max, int action)
{
        bool success;
        int core;
        union kvmppc_rm_state old, new;

        for (core = start + 1; core < max; core++)  {
                old = new = READ_ONCE(rm_core[core].rm_state);

                if (!old.in_host || old.rm_action)
                        continue;

                /* Try to grab this host core if not taken already. */
                new.rm_action = action;

                success = cmpxchg64(&rm_core[core].rm_state.raw,
                                                old.raw, new.raw) == old.raw;
                if (success) {
                        /*
                         * Make sure that the store to the rm_action is made
                         * visible before we return to caller (and the
                         * subsequent store to rm_data) to synchronize with
                         * the IPI handler.
                         */
                        smp_wmb();
                        return core;
                }
        }

        return -1;
}

static inline int find_available_hostcore(int action)
{
        int core;
        int my_core = smp_processor_id() >> threads_shift;
        struct kvmppc_host_rm_core *rm_core = kvmppc_host_rm_ops_hv->rm_core;

        core = grab_next_hostcore(my_core, rm_core, cpu_nr_cores(), action);
        if (core == -1)
                core = grab_next_hostcore(core, rm_core, my_core, action);

        return core;
}

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;
        int cpu;
        int hcore;

        /* Mark the target VCPU as having an interrupt pending */
        vcpu->stat.queue_intr++;
        set_bit(BOOK3S_IRQPRIO_EXTERNAL, &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, find an available host core to post to wake the VCPU,
         * if we can't find one, set up state to eventually return too hard.
         */
        cpu = vcpu->arch.thread_cpu;
        if (cpu < 0 || cpu >= nr_cpu_ids) {
                hcore = -1;
                if (kvmppc_host_rm_ops_hv && h_ipi_redirect)
                        hcore = find_available_hostcore(XICS_RM_KICK_VCPU);
                if (hcore != -1) {
                        icp_send_hcore_msg(hcore, vcpu);
                } else {
                        this_icp->rm_action |= XICS_RM_KICK_VCPU;
                        this_icp->rm_kick_target = vcpu;
                }
                return;
        }

        smp_mb();
        kvmhv_rm_send_ipi(cpu);
}

static void icp_rm_clr_vcpu_irq(struct kvm_vcpu *vcpu)
{
        /* Note: Only called on self ! */
        clear_bit(BOOK3S_IRQPRIO_EXTERNAL, &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_check_resend(struct kvmppc_xics *xics,
                             struct kvmppc_icp *icp)
{
        u32 icsid;

        /* Order this load with the test for need_resend in the caller */
        smp_rmb();
        for_each_set_bit(icsid, icp->resend_map, xics->max_icsid + 1) {
                struct kvmppc_ics *ics = xics->ics[icsid];

                if (!test_and_clear_bit(icsid, icp->resend_map))
                        continue;
                if (!ics)
                        continue;
                ics_rm_check_resend(xics, ics, icp);
        }
}

static bool icp_rm_try_to_deliver(struct kvmppc_icp *icp, u32 irq, u8 priority,
                               u32 *reject)
{
        union kvmppc_icp_state old_state, new_state;
        bool success;

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

                *reject = 0;

                /* See if we can deliver */
                success = new_state.cppr > priority &&
                        new_state.mfrr > priority &&
                        new_state.pending_pri > priority;

                /*
                 * If we can, check for a rejection and perform the
                 * delivery
                 */
                if (success) {
                        *reject = new_state.xisr;
                        new_state.xisr = irq;
                        new_state.pending_pri = priority;
                } else {
                        /*
                         * If we failed to deliver we set need_resend
                         * so a subsequent CPPR state change causes us
                         * to try a new delivery.
                         */
                        new_state.need_resend = true;
                }

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

        return success;
}

static void icp_rm_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
                            u32 new_irq, bool check_resend)
{
        struct ics_irq_state *state;
        struct kvmppc_ics *ics;
        u32 reject;
        u16 src;

        /*
         * This is used both for initial delivery of an interrupt and
         * for subsequent rejection.
         *
         * Rejection can be racy vs. resends. We have evaluated the
         * rejection in an atomic ICP transaction which is now complete,
         * so potentially the ICP can already accept the interrupt again.
         *
         * So we need to retry the delivery. Essentially the reject path
         * boils down to a failed delivery. Always.
         *
         * Now the interrupt could also have moved to a different target,
         * thus we may need to re-do the ICP lookup as well
         */

 again:
        /* Get the ICS state and lock it */
        ics = kvmppc_xics_find_ics(xics, new_irq, &src);
        if (!ics) {
                /* Unsafe increment, but this does not need to be accurate */
                xics->err_noics++;
                return;
        }
        state = &ics->irq_state[src];

        /* Get a lock on the ICS */
        arch_spin_lock(&ics->lock);

        /* Get our server */
        if (!icp || state->server != icp->server_num) {
                icp = kvmppc_xics_find_server(xics->kvm, state->server);
                if (!icp) {
                        /* Unsafe increment again*/
                        xics->err_noicp++;
                        goto out;
                }
        }

        if (check_resend)
                if (!state->resend)
                        goto out;

        /* Clear the resend bit of that interrupt */
        state->resend = 0;

        /*
         * If masked, bail out
         *
         * Note: PAPR doesn't mention anything about masked pending
         * when doing a resend, only when doing a delivery.
         *
         * However that would have the effect of losing a masked
         * interrupt that was rejected and isn't consistent with
         * the whole masked_pending business which is about not
         * losing interrupts that occur while masked.
         *
         * I don't differentiate normal deliveries and resends, this
         * implementation will differ from PAPR and not lose such
         * interrupts.
         */
        if (state->priority == MASKED) {
                state->masked_pending = 1;
                goto out;
        }

        /*
         * Try the delivery, this will set the need_resend flag
         * in the ICP as part of the atomic transaction if the
         * delivery is not possible.
         *
         * Note that if successful, the new delivery might have itself
         * rejected an interrupt that was "delivered" before we took the
         * ics spin lock.
         *
         * In this case we do the whole sequence all over again for the
         * new guy. We cannot assume that the rejected interrupt is less
         * favored than the new one, and thus doesn't need to be delivered,
         * because by the time we exit icp_rm_try_to_deliver() the target
         * processor may well have already consumed & completed it, and thus
         * the rejected interrupt might actually be already acceptable.
         */
        if (icp_rm_try_to_deliver(icp, new_irq, state->priority, &reject)) {
                /*
                 * Delivery was successful, did we reject somebody else ?
                 */
                if (reject && reject != XICS_IPI) {
                        arch_spin_unlock(&ics->lock);
                        icp->n_reject++;
                        new_irq = reject;
                        check_resend = 0;
                        goto again;
                }
        } else {
                /*
                 * We failed to deliver the interrupt we need to set the
                 * resend map bit and mark the ICS state as needing a resend
                 */
                state->resend = 1;

                /*
                 * Make sure when checking resend, we don't miss the resend
                 * if resend_map bit is seen and cleared.
                 */
                smp_wmb();
                set_bit(ics->icsid, icp->resend_map);

                /*
                 * If the need_resend flag got cleared in the ICP some time
                 * between icp_rm_try_to_deliver() atomic update and now, then
                 * we know it might have missed the resend_map bit. So we
                 * retry
                 */
                smp_mb();
                if (!icp->state.need_resend) {
                        state->resend = 0;
                        arch_spin_unlock(&ics->lock);
                        check_resend = 0;
                        goto again;
                }
        }
 out:
        arch_spin_unlock(&ics->lock);
}

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 = READ_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->n_check_resend++;
                icp_rm_check_resend(xics, icp);
        }
}


unsigned long xics_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 = READ_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.regs.gpr[4] = xirr;

        return check_too_hard(xics, icp);
}

int xics_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.
         *
         * ICP state: Check_IPI
         *
         * If the CPPR is less favored, then we might be replacing
         * an interrupt, and thus need to possibly reject it.
         *
         * ICP State: IPI
         *
         * Besides rejecting any pending interrupts, we also
         * update XISR and pending_pri to mark IPI as pending.
         *
         * PAPR does not describe this state, but if the MFRR is being
         * made less favored than its earlier value, there might be
         * a previously-rejected interrupt needing to be resent.
         * Ideally, we would want to resend only if
         *      prio(pending_interrupt) < mfrr &&
         *      prio(pending_interrupt) < cppr
         * where pending interrupt is the one that was rejected. But
         * we don't have that state, so we simply trigger a resend
         * whenever the MFRR is made less favored.
         */
        do {
                old_state = new_state = READ_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) {
                        resend = new_state.need_resend;
                        new_state.need_resend = 0;
                }
        } while (!icp_rm_try_update(icp, old_state, new_state));

        /* Handle reject in real mode */
        if (reject && reject != XICS_IPI) {
                this_icp->n_reject++;
                icp_rm_deliver_irq(xics, icp, reject, false);
        }

        /* Handle resends in real mode */
        if (resend) {
                this_icp->n_check_resend++;
                icp_rm_check_resend(xics, icp);
        }

        return check_too_hard(xics, this_icp);
}

int xics_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 = READ_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));

        /*
         * Check for rejects. They are handled by doing a new delivery
         * attempt (see comments in icp_rm_deliver_irq).
         */
        if (reject && reject != XICS_IPI) {
                icp->n_reject++;
                icp_rm_deliver_irq(xics, icp, reject, false);
        }
 bail:
        return check_too_hard(xics, icp);
}

static int ics_rm_eoi(struct kvm_vcpu *vcpu, u32 irq)
{
        struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
        struct kvmppc_icp *icp = vcpu->arch.icp;
        struct kvmppc_ics *ics;
        struct ics_irq_state *state;
        u16 src;
        u32 pq_old, pq_new;

        /*
         * ICS EOI handling: For LSI, if P bit is still set, we need to
         * resend it.
         *
         * For MSI, we move Q bit into P (and clear Q). If it is set,
         * resend it.
         */

        ics = kvmppc_xics_find_ics(xics, irq, &src);
        if (!ics)
                goto bail;

        state = &ics->irq_state[src];

        if (state->lsi)
                pq_new = state->pq_state;
        else
                do {
                        pq_old = state->pq_state;
                        pq_new = pq_old >> 1;
                } while (cmpxchg(&state->pq_state, pq_old, pq_new) != pq_old);

        if (pq_new & PQ_PRESENTED)
                icp_rm_deliver_irq(xics, NULL, irq, false);

        if (!hlist_empty(&vcpu->kvm->irq_ack_notifier_list)) {
                icp->rm_action |= XICS_RM_NOTIFY_EOI;
                icp->rm_eoied_irq = irq;
        }

        if (state->host_irq) {
                ++vcpu->stat.pthru_all;
                if (state->intr_cpu != -1) {
                        int pcpu = raw_smp_processor_id();

                        pcpu = cpu_first_thread_sibling(pcpu);
                        ++vcpu->stat.pthru_host;
                        if (state->intr_cpu != pcpu) {
                                ++vcpu->stat.pthru_bad_aff;
                                xics_opal_set_server(state->host_irq, pcpu);
                        }
                        state->intr_cpu = -1;
                }
        }

 bail:
        return check_too_hard(xics, icp);
}

int xics_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;
        u32 irq = xirr & 0x00ffffff;

        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 specifies
         * 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)
                return check_too_hard(xics, icp);

        return ics_rm_eoi(vcpu, irq);
}

static unsigned long eoi_rc;

static void icp_eoi(struct irq_chip *c, u32 hwirq, __be32 xirr, bool *again)
{
        void __iomem *xics_phys;
        int64_t rc;

        rc = pnv_opal_pci_msi_eoi(c, hwirq);

        if (rc)
                eoi_rc = rc;

        iosync();

        /* EOI it */
        xics_phys = local_paca->kvm_hstate.xics_phys;
        if (xics_phys) {
                __raw_rm_writel(xirr, xics_phys + XICS_XIRR);
        } else {
                rc = opal_int_eoi(be32_to_cpu(xirr));
                *again = rc > 0;
        }
}

static int xics_opal_set_server(unsigned int hw_irq, int server_cpu)
{
        unsigned int mangle_cpu = get_hard_smp_processor_id(server_cpu) << 2;

        return opal_set_xive(hw_irq, mangle_cpu, DEFAULT_PRIORITY);
}

/*
 * Increment a per-CPU 32-bit unsigned integer variable.
 * Safe to call in real-mode. Handles vmalloc'ed addresses
 *
 * ToDo: Make this work for any integral type
 */

static inline void this_cpu_inc_rm(unsigned int __percpu *addr)
{
        unsigned long l;
        unsigned int *raddr;
        int cpu = smp_processor_id();

        raddr = per_cpu_ptr(addr, cpu);
        l = (unsigned long)raddr;

        if (get_region_id(l) == VMALLOC_REGION_ID) {
                l = vmalloc_to_phys(raddr);
                raddr = (unsigned int *)l;
        }
        ++*raddr;
}

/*
 * We don't try to update the flags in the irq_desc 'istate' field in
 * here as would happen in the normal IRQ handling path for several reasons:
 *  - state flags represent internal IRQ state and are not expected to be
 *    updated outside the IRQ subsystem
 *  - more importantly, these are useful for edge triggered interrupts,
 *    IRQ probing, etc., but we are only handling MSI/MSIx interrupts here
 *    and these states shouldn't apply to us.
 *
 * However, we do update irq_stats - we somewhat duplicate the code in
 * kstat_incr_irqs_this_cpu() for this since this function is defined
 * in irq/internal.h which we don't want to include here.
 * The only difference is that desc->kstat_irqs is an allocated per CPU
 * variable and could have been vmalloc'ed, so we can't directly
 * call __this_cpu_inc() on it. The kstat structure is a static
 * per CPU variable and it should be accessible by real-mode KVM.
 *
 */
static void kvmppc_rm_handle_irq_desc(struct irq_desc *desc)
{
        this_cpu_inc_rm(desc->kstat_irqs);
        __this_cpu_inc(kstat.irqs_sum);
}

long kvmppc_deliver_irq_passthru(struct kvm_vcpu *vcpu,
                                 __be32 xirr,
                                 struct kvmppc_irq_map *irq_map,
                                 struct kvmppc_passthru_irqmap *pimap,
                                 bool *again)
{
        struct kvmppc_xics *xics;
        struct kvmppc_icp *icp;
        struct kvmppc_ics *ics;
        struct ics_irq_state *state;
        u32 irq;
        u16 src;
        u32 pq_old, pq_new;

        irq = irq_map->v_hwirq;
        xics = vcpu->kvm->arch.xics;
        icp = vcpu->arch.icp;

        kvmppc_rm_handle_irq_desc(irq_map->desc);

        ics = kvmppc_xics_find_ics(xics, irq, &src);
        if (!ics)
                return 2;

        state = &ics->irq_state[src];

        /* only MSIs register bypass producers, so it must be MSI here */
        do {
                pq_old = state->pq_state;
                pq_new = ((pq_old << 1) & 3) | PQ_PRESENTED;
        } while (cmpxchg(&state->pq_state, pq_old, pq_new) != pq_old);

        /* Test P=1, Q=0, this is the only case where we present */
        if (pq_new == PQ_PRESENTED)
                icp_rm_deliver_irq(xics, icp, irq, false);

        /* EOI the interrupt */
        icp_eoi(irq_desc_get_chip(irq_map->desc), irq_map->r_hwirq, xirr,
                again);

        if (check_too_hard(xics, icp) == H_TOO_HARD)
                return 2;
        else
                return -2;
}

/*  --- Non-real mode XICS-related built-in routines ---  */

/**
 * Host Operations poked by RM KVM
 */
static void rm_host_ipi_action(int action, void *data)
{
        switch (action) {
        case XICS_RM_KICK_VCPU:
                kvmppc_host_rm_ops_hv->vcpu_kick(data);
                break;
        default:
                WARN(1, "Unexpected rm_action=%d data=%p\n", action, data);
                break;
        }

}

void kvmppc_xics_ipi_action(void)
{
        int core;
        unsigned int cpu = smp_processor_id();
        struct kvmppc_host_rm_core *rm_corep;

        core = cpu >> threads_shift;
        rm_corep = &kvmppc_host_rm_ops_hv->rm_core[core];

        if (rm_corep->rm_data) {
                rm_host_ipi_action(rm_corep->rm_state.rm_action,
                                                        rm_corep->rm_data);
                /* Order these stores against the real mode KVM */
                rm_corep->rm_data = NULL;
                smp_wmb();
                rm_corep->rm_state.rm_action = 0;
        }
}