vgic-v4.c

Go to the documentation of this file.

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2017 ARM Ltd.
 * Author: Marc Zyngier <marc.zyngier@arm.com>
 */
 
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/kvm_host.h>
#include <linux/irqchip/arm-gic-v3.h>
 
#include "vgic.h"
 
/*
 * How KVM uses GICv4 (insert rude comments here):
 *
 * The vgic-v4 layer acts as a bridge between several entities:
 * - The GICv4 ITS representation offered by the ITS driver
 * - VFIO, which is in charge of the PCI endpoint
 * - The virtual ITS, which is the only thing the guest sees
 *
 * The configuration of VLPIs is triggered by a callback from VFIO,
 * instructing KVM that a PCI device has been configured to deliver
 * MSIs to a vITS.
 *
 * kvm_vgic_v4_set_forwarding() is thus called with the routing entry,
 * and this is used to find the corresponding vITS data structures
 * (ITS instance, device, event and irq) using a process that is
 * extremely similar to the injection of an MSI.
 *
 * At this stage, we can link the guest's view of an LPI (uniquely
 * identified by the routing entry) and the host irq, using the GICv4
 * driver mapping operation. Should the mapping succeed, we've then
 * successfully upgraded the guest's LPI to a VLPI. We can then start
 * with updating GICv4's view of the property table and generating an
 * INValidation in order to kickstart the delivery of this VLPI to the
 * guest directly, without software intervention. Well, almost.
 *
 * When the PCI endpoint is deconfigured, this operation is reversed
 * with VFIO calling kvm_vgic_v4_unset_forwarding().
 *
 * Once the VLPI has been mapped, it needs to follow any change the
 * guest performs on its LPI through the vITS. For that, a number of
 * command handlers have hooks to communicate these changes to the HW:
 * - Any invalidation triggers a call to its_prop_update_vlpi()
 * - The INT command results in a irq_set_irqchip_state(), which
 *   generates an INT on the corresponding VLPI.
 * - The CLEAR command results in a irq_set_irqchip_state(), which
 *   generates an CLEAR on the corresponding VLPI.
 * - DISCARD translates into an unmap, similar to a call to
 *   kvm_vgic_v4_unset_forwarding().
 * - MOVI is translated by an update of the existing mapping, changing
 *   the target vcpu, resulting in a VMOVI being generated.
 * - MOVALL is translated by a string of mapping updates (similar to
 *   the handling of MOVI). MOVALL is horrible.
 *
 * Note that a DISCARD/MAPTI sequence emitted from the guest without
 * reprogramming the PCI endpoint after MAPTI does not result in a
 * VLPI being mapped, as there is no callback from VFIO (the guest
 * will get the interrupt via the normal SW injection). Fixing this is
 * not trivial, and requires some horrible messing with the VFIO
 * internals. Not fun. Don't do that.
 *
 * Then there is the scheduling. Each time a vcpu is about to run on a
 * physical CPU, KVM must tell the corresponding redistributor about
 * it. And if we've migrated our vcpu from one CPU to another, we must
 * tell the ITS (so that the messages reach the right redistributor).
 * This is done in two steps: first issue a irq_set_affinity() on the
 * irq corresponding to the vcpu, then call its_make_vpe_resident().
 * You must be in a non-preemptible context. On exit, a call to
 * its_make_vpe_non_resident() tells the redistributor that we're done
 * with the vcpu.
 *
 * Finally, the doorbell handling: Each vcpu is allocated an interrupt
 * which will fire each time a VLPI is made pending whilst the vcpu is
 * not running. Each time the vcpu gets blocked, the doorbell
 * interrupt gets enabled. When the vcpu is unblocked (for whatever
 * reason), the doorbell interrupt is disabled.
 */
 
#define DB_IRQ_FLAGS    (IRQ_NOAUTOEN | IRQ_DISABLE_UNLAZY | IRQ_NO_BALANCING)
 
static irqreturn_t vgic_v4_doorbell_handler(int irq, void *info)
{
    struct kvm_vcpu *vcpu = info;
 
    /* We got the message, no need to fire again */
    if (!kvm_vgic_global_state.has_gicv4_1 &&
        !irqd_irq_disabled(&irq_to_desc(irq)->irq_data))
        disable_irq_nosync(irq);
 
    /*
     * The v4.1 doorbell can fire concurrently with the vPE being
     * made non-resident. Ensure we only update pending_last
     * *after* the non-residency sequence has completed.
     */
    raw_spin_lock(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vpe_lock);
    vcpu->arch.vgic_cpu.vgic_v3.its_vpe.pending_last = true;
    raw_spin_unlock(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vpe_lock);
 
    kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
    kvm_vcpu_kick(vcpu);
 
    return IRQ_HANDLED;
}
 
static void vgic_v4_sync_sgi_config(struct its_vpe *vpe, struct vgic_irq *irq)
{
    vpe->sgi_config[irq->intid].enabled = irq->enabled;
    vpe->sgi_config[irq->intid].group   = irq->group;
    vpe->sgi_config[irq->intid].priority    = irq->priority;
}
 
static void vgic_v4_enable_vsgis(struct kvm_vcpu *vcpu)
{
    struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
    int i;
 
    /*
     * With GICv4.1, every virtual SGI can be directly injected. So
     * let's pretend that they are HW interrupts, tied to a host
     * IRQ. The SGI code will do its magic.
     */
    for (i = 0; i < VGIC_NR_SGIS; i++) {
        struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, i);
        struct irq_desc *desc;
        unsigned long flags;
        int ret;
 
        raw_spin_lock_irqsave(&irq->irq_lock, flags);
 
        if (irq->hw)
            goto unlock;
 
        irq->hw = true;
        irq->host_irq = irq_find_mapping(vpe->sgi_domain, i);
 
        /* Transfer the full irq state to the vPE */
        vgic_v4_sync_sgi_config(vpe, irq);
        desc = irq_to_desc(irq->host_irq);
        ret = irq_domain_activate_irq(irq_desc_get_irq_data(desc),
                          false);
        if (!WARN_ON(ret)) {
            /* Transfer pending state */
            ret = irq_set_irqchip_state(irq->host_irq,
                            IRQCHIP_STATE_PENDING,
                            irq->pending_latch);
            WARN_ON(ret);
            irq->pending_latch = false;
        }
    unlock:
        raw_spin_unlock_irqrestore(&irq->irq_lock, flags);
        vgic_put_irq(vcpu->kvm, irq);
    }
}
 
static void vgic_v4_disable_vsgis(struct kvm_vcpu *vcpu)
{
    int i;
 
    for (i = 0; i < VGIC_NR_SGIS; i++) {
        struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, i);
        struct irq_desc *desc;
        unsigned long flags;
        int ret;
 
        raw_spin_lock_irqsave(&irq->irq_lock, flags);
 
        if (!irq->hw)
            goto unlock;
 
        irq->hw = false;
        ret = irq_get_irqchip_state(irq->host_irq,
                        IRQCHIP_STATE_PENDING,
                        &irq->pending_latch);
        WARN_ON(ret);
 
        desc = irq_to_desc(irq->host_irq);
        irq_domain_deactivate_irq(irq_desc_get_irq_data(desc));
    unlock:
        raw_spin_unlock_irqrestore(&irq->irq_lock, flags);
        vgic_put_irq(vcpu->kvm, irq);
    }
}
 
void vgic_v4_configure_vsgis(struct kvm *kvm)
{
    struct vgic_dist *dist = &kvm->arch.vgic;
    struct kvm_vcpu *vcpu;
    unsigned long i;
 
    lockdep_assert_held(&kvm->arch.config_lock);
 
    kvm_arm_halt_guest(kvm);
 
    kvm_for_each_vcpu(i, vcpu, kvm) {
        if (dist->nassgireq)
            vgic_v4_enable_vsgis(vcpu);
        else
            vgic_v4_disable_vsgis(vcpu);
    }
 
    kvm_arm_resume_guest(kvm);
}
 
/*
 * Must be called with GICv4.1 and the vPE unmapped, which
 * indicates the invalidation of any VPT caches associated
 * with the vPE, thus we can get the VLPI state by peeking
 * at the VPT.
 */
void vgic_v4_get_vlpi_state(struct vgic_irq *irq, bool *val)
{
    struct its_vpe *vpe = &irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
    int mask = BIT(irq->intid % BITS_PER_BYTE);
    void *va;
    u8 *ptr;
 
    va = page_address(vpe->vpt_page);
    ptr = va + irq->intid / BITS_PER_BYTE;
 
    *val = !!(*ptr & mask);
}
 
int vgic_v4_request_vpe_irq(struct kvm_vcpu *vcpu, int irq)
{
    return request_irq(irq, vgic_v4_doorbell_handler, 0, "vcpu", vcpu);
}
 
/**
 * vgic_v4_init - Initialize the GICv4 data structures
 * @kvm:    Pointer to the VM being initialized
 *
 * We may be called each time a vITS is created, or when the
 * vgic is initialized. In both cases, the number of vcpus
 * should now be fixed.
 */
int vgic_v4_init(struct kvm *kvm)
{
    struct vgic_dist *dist = &kvm->arch.vgic;
    struct kvm_vcpu *vcpu;
    int nr_vcpus, ret;
    unsigned long i;
 
    lockdep_assert_held(&kvm->arch.config_lock);
 
    if (!kvm_vgic_global_state.has_gicv4)
        return 0; /* Nothing to see here... move along. */
 
    if (dist->its_vm.vpes)
        return 0;
 
    nr_vcpus = atomic_read(&kvm->online_vcpus);
 
    dist->its_vm.vpes = kcalloc(nr_vcpus, sizeof(*dist->its_vm.vpes),
                    GFP_KERNEL_ACCOUNT);
    if (!dist->its_vm.vpes)
        return -ENOMEM;
 
    dist->its_vm.nr_vpes = nr_vcpus;
 
    kvm_for_each_vcpu(i, vcpu, kvm)
        dist->its_vm.vpes[i] = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
 
    ret = its_alloc_vcpu_irqs(&dist->its_vm);
    if (ret < 0) {
        kvm_err("VPE IRQ allocation failure\n");
        kfree(dist->its_vm.vpes);
        dist->its_vm.nr_vpes = 0;
        dist->its_vm.vpes = NULL;
        return ret;
    }
 
    kvm_for_each_vcpu(i, vcpu, kvm) {
        int irq = dist->its_vm.vpes[i]->irq;
        unsigned long irq_flags = DB_IRQ_FLAGS;
 
        /*
         * Don't automatically enable the doorbell, as we're
         * flipping it back and forth when the vcpu gets
         * blocked. Also disable the lazy disabling, as the
         * doorbell could kick us out of the guest too
         * early...
         *
         * On GICv4.1, the doorbell is managed in HW and must
         * be left enabled.
         */
        if (kvm_vgic_global_state.has_gicv4_1)
            irq_flags &= ~IRQ_NOAUTOEN;
        irq_set_status_flags(irq, irq_flags);
 
        ret = vgic_v4_request_vpe_irq(vcpu, irq);
        if (ret) {
            kvm_err("failed to allocate vcpu IRQ%d\n", irq);
            /*
             * Trick: adjust the number of vpes so we know
             * how many to nuke on teardown...
             */
            dist->its_vm.nr_vpes = i;
            break;
        }
    }
 
    if (ret)
        vgic_v4_teardown(kvm);
 
    return ret;
}
 
/**
 * vgic_v4_teardown - Free the GICv4 data structures
 * @kvm:    Pointer to the VM being destroyed
 */
void vgic_v4_teardown(struct kvm *kvm)
{
    struct its_vm *its_vm = &kvm->arch.vgic.its_vm;
    int i;
 
    lockdep_assert_held(&kvm->arch.config_lock);
 
    if (!its_vm->vpes)
        return;
 
    for (i = 0; i < its_vm->nr_vpes; i++) {
        struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, i);
        int irq = its_vm->vpes[i]->irq;
 
        irq_clear_status_flags(irq, DB_IRQ_FLAGS);
        free_irq(irq, vcpu);
    }
 
    its_free_vcpu_irqs(its_vm);
    kfree(its_vm->vpes);
    its_vm->nr_vpes = 0;
    its_vm->vpes = NULL;
}
 
int vgic_v4_put(struct kvm_vcpu *vcpu)
{
    struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
 
    if (!vgic_supports_direct_msis(vcpu->kvm) || !vpe->resident)
        return 0;
 
    return its_make_vpe_non_resident(vpe, !!vcpu_get_flag(vcpu, IN_WFI));
}
 
int vgic_v4_load(struct kvm_vcpu *vcpu)
{
    struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
    int err;
 
    if (!vgic_supports_direct_msis(vcpu->kvm) || vpe->resident)
        return 0;
 
    if (vcpu_get_flag(vcpu, IN_WFI))
        return 0;
 
    /*
     * Before making the VPE resident, make sure the redistributor
     * corresponding to our current CPU expects us here. See the
     * doc in drivers/irqchip/irq-gic-v4.c to understand how this
     * turns into a VMOVP command at the ITS level.
     */
    err = irq_set_affinity(vpe->irq, cpumask_of(smp_processor_id()));
    if (err)
        return err;
 
    err = its_make_vpe_resident(vpe, false, vcpu->kvm->arch.vgic.enabled);
    if (err)
        return err;
 
    /*
     * Now that the VPE is resident, let's get rid of a potential
     * doorbell interrupt that would still be pending. This is a
     * GICv4.0 only "feature"...
     */
    if (!kvm_vgic_global_state.has_gicv4_1)
        err = irq_set_irqchip_state(vpe->irq, IRQCHIP_STATE_PENDING, false);
 
    return err;
}
 
void vgic_v4_commit(struct kvm_vcpu *vcpu)
{
    struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
 
    /*
     * No need to wait for the vPE to be ready across a shallow guest
     * exit, as only a vcpu_put will invalidate it.
     */
    if (!vpe->ready)
        its_commit_vpe(vpe);
}
 
static struct vgic_its *vgic_get_its(struct kvm *kvm,
                     struct kvm_kernel_irq_routing_entry *irq_entry)
{
    struct kvm_msi msi  = (struct kvm_msi) {
        .address_lo = irq_entry->msi.address_lo,
        .address_hi = irq_entry->msi.address_hi,
        .data       = irq_entry->msi.data,
        .flags      = irq_entry->msi.flags,
        .devid      = irq_entry->msi.devid,
    };
 
    return vgic_msi_to_its(kvm, &msi);
}
 
int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
                   struct kvm_kernel_irq_routing_entry *irq_entry)
{
    struct vgic_its *its;
    struct vgic_irq *irq;
    struct its_vlpi_map map;
    unsigned long flags;
    int ret;
 
    if (!vgic_supports_direct_msis(kvm))
        return 0;
 
    /*
     * Get the ITS, and escape early on error (not a valid
     * doorbell for any of our vITSs).
     */
    its = vgic_get_its(kvm, irq_entry);
    if (IS_ERR(its))
        return 0;
 
    mutex_lock(&its->its_lock);
 
    /* Perform the actual DevID/EventID -> LPI translation. */
    ret = vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid,
                   irq_entry->msi.data, &irq);
    if (ret)
        goto out;
 
    /* Silently exit if the vLPI is already mapped */
    if (irq->hw)
        goto out;
 
    /*
     * Emit the mapping request. If it fails, the ITS probably
     * isn't v4 compatible, so let's silently bail out. Holding
     * the ITS lock should ensure that nothing can modify the
     * target vcpu.
     */
    map = (struct its_vlpi_map) {
        .vm     = &kvm->arch.vgic.its_vm,
        .vpe        = &irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe,
        .vintid     = irq->intid,
        .properties = ((irq->priority & 0xfc) |
                   (irq->enabled ? LPI_PROP_ENABLED : 0) |
                   LPI_PROP_GROUP1),
        .db_enabled = true,
    };
 
    ret = its_map_vlpi(virq, &map);
    if (ret)
        goto out;
 
    irq->hw     = true;
    irq->host_irq   = virq;
    atomic_inc(&map.vpe->vlpi_count);
 
    /* Transfer pending state */
    raw_spin_lock_irqsave(&irq->irq_lock, flags);
    if (irq->pending_latch) {
        ret = irq_set_irqchip_state(irq->host_irq,
                        IRQCHIP_STATE_PENDING,
                        irq->pending_latch);
        WARN_RATELIMIT(ret, "IRQ %d", irq->host_irq);
 
        /*
         * Clear pending_latch and communicate this state
         * change via vgic_queue_irq_unlock.
         */
        irq->pending_latch = false;
        vgic_queue_irq_unlock(kvm, irq, flags);
    } else {
        raw_spin_unlock_irqrestore(&irq->irq_lock, flags);
    }
 
out:
    mutex_unlock(&its->its_lock);
    return ret;
}
 
int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int virq,
                 struct kvm_kernel_irq_routing_entry *irq_entry)
{
    struct vgic_its *its;
    struct vgic_irq *irq;
    int ret;
 
    if (!vgic_supports_direct_msis(kvm))
        return 0;
 
    /*
     * Get the ITS, and escape early on error (not a valid
     * doorbell for any of our vITSs).
     */
    its = vgic_get_its(kvm, irq_entry);
    if (IS_ERR(its))
        return 0;
 
    mutex_lock(&its->its_lock);
 
    ret = vgic_its_resolve_lpi(kvm, its, irq_entry->msi.devid,
                   irq_entry->msi.data, &irq);
    if (ret)
        goto out;
 
    WARN_ON(!(irq->hw && irq->host_irq == virq));
    if (irq->hw) {
        atomic_dec(&irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count);
        irq->hw = false;
        ret = its_unmap_vlpi(virq);
    }
 
out:
    mutex_unlock(&its->its_lock);
    return ret;
}