Re: [PATCH v3 41/59] KVM: arm/arm64: GICv4: Wire mapping/unmapping of VLPIs in VFIO irq bypass

Christoffer Dall
2017-08-30T11:46:46Z

On Wed, Aug 30, 2017 at 11:28:08AM +0100, Marc Zyngier wrote:
> On 26/08/17 20:48, Christoffer Dall wrote:
> > On Mon, Jul 31, 2017 at 06:26:19PM +0100, Marc Zyngier wrote:
> >> Let's use the irq bypass mechanism introduced for platform device
> >> interrupts to intercept the virtual PCIe endpoint configuration
> >> and establish our LPI->VLPI mapping.
> >>
> >> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> >> ---
> >> include/kvm/arm_vgic.h | 8 ++++
> >> virt/kvm/arm/arm.c | 27 ++++++++----
> >> virt/kvm/arm/vgic/vgic-v4.c | 103 ++++++++++++++++++++++++++++++++++++++++++++
> >> 3 files changed, 130 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> >> index 359eeffe9857..050f78d4fb42 100644
> >> --- a/include/kvm/arm_vgic.h
> >> +++ b/include/kvm/arm_vgic.h
> >> @@ -367,4 +367,12 @@ int kvm_vgic_set_forwarding(struct kvm *kvm, unsigned int host_irq,
> >> void kvm_vgic_unset_forwarding(struct kvm *kvm, unsigned int host_irq,
> >> unsigned int vintid);
> >>
> >> +struct kvm_kernel_irq_routing_entry;
> >> +
> >> +int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int irq,
> >> + struct kvm_kernel_irq_routing_entry *irq_entry);
> >> +
> >> +int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int irq,
> >> + struct kvm_kernel_irq_routing_entry *irq_entry);
> >> +
> >> #endif /* __KVM_ARM_VGIC_H */
> >> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> >> index ebab6c29e3be..6803ea27c47d 100644
> >> --- a/virt/kvm/arm/arm.c
> >> +++ b/virt/kvm/arm/arm.c
> >> @@ -1457,11 +1457,16 @@ int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *cons,
> >> struct kvm_kernel_irqfd *irqfd =
> >> container_of(cons, struct kvm_kernel_irqfd, consumer);
> >>
> >> - if (prod->type != IRQ_BYPASS_VFIO_PLATFORM)
> >> + switch (prod->type) {
> >> + case IRQ_BYPASS_VFIO_PLATFORM:
> >> + return kvm_vgic_set_forwarding(irqfd->kvm, prod->irq,
> >> + irqfd->gsi + VGIC_NR_PRIVATE_IRQS);
> >> + case IRQ_BYPASS_VFIO_PCI_MSI:
> >> + return kvm_vgic_v4_set_forwarding(irqfd->kvm, prod->irq,
> >> + &irqfd->irq_entry);
> >> + default:
> >> return 0;
> >> -
> >> - return kvm_vgic_set_forwarding(irqfd->kvm, prod->irq,
> >> - irqfd->gsi + VGIC_NR_PRIVATE_IRQS);
> >> + }
> >> }
> >> void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
> >> struct irq_bypass_producer *prod)
> >> @@ -1469,11 +1474,17 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
> >> struct kvm_kernel_irqfd *irqfd =
> >> container_of(cons, struct kvm_kernel_irqfd, consumer);
> >>
> >> - if (prod->type != IRQ_BYPASS_VFIO_PLATFORM)
> >> - return;
> >> + switch (prod->type) {
> >> + case IRQ_BYPASS_VFIO_PLATFORM:
> >> + kvm_vgic_unset_forwarding(irqfd->kvm, prod->irq,
> >> + irqfd->gsi + VGIC_NR_PRIVATE_IRQS);
> >> + break;
> >>
> >> - kvm_vgic_unset_forwarding(irqfd->kvm, prod->irq,
> >> - irqfd->gsi + VGIC_NR_PRIVATE_IRQS);
> >> + case IRQ_BYPASS_VFIO_PCI_MSI:
> >> + kvm_vgic_v4_unset_forwarding(irqfd->kvm, prod->irq,
> >> + &irqfd->irq_entry);
> >> + break;
> >> + }
> >> }
> >>
> >> void kvm_arch_irq_bypass_stop(struct irq_bypass_consumer *cons)
> >> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
> >> index 207e1fda0dcd..338c86c5159f 100644
> >> --- a/virt/kvm/arm/vgic/vgic-v4.c
> >> +++ b/virt/kvm/arm/vgic/vgic-v4.c
> >> @@ -72,3 +72,106 @@ void vgic_v4_teardown(struct kvm *kvm)
> >> its_vm->nr_vpes = 0;
> >> its_vm->vpes = NULL;
> >> }
> >> +
> >> +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,
> >> + };
> >> +
> >> + /*
> >> + * Get a reference on the LPI. If NULL, this is not a valid
> >> + * translation for any of our vITSs.
> >> + */
> >> + 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;
> >> + int ret;
> >> +
> >> + if (!vgic_is_v4_capable(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 then 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;
> >> +
> >> + /*
> >> + * 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,
> >> + .vintid = irq->intid,
> >> + .db_enabled = true,
> >> + .vpe_idx = irq->target_vcpu->vcpu_id,
>
> This is just wrong. We cannot assume that the vcpu_id has anything to do
> with the vpe_idx. It happens to be the same thing now, but the two things
> should be clearly disconnected.
>
> I suggest the following (untested):
>
> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
> index cf5d6e2de6b8..0146e004401a 100644
> --- a/virt/kvm/arm/vgic/vgic-v4.c
> +++ b/virt/kvm/arm/vgic/vgic-v4.c
> @@ -251,13 +251,27 @@ static void dump_routing(int virq, struct kvm_kernel_irq_routing_entry *irq_entr
>
> }
>
> +static int vgic_v4_vcpu_to_index(struct its_vm *its_vm, struct kvm_vcpu *vcpu)
> +{
> + int i;
> +
> + for (i = 0; i < its_vm->nr_vpes; i++) {
> + struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
> +
> + if (its_vm->vpes[i] == vpe)
> + return i;
> + }
> +
> + return -ENODEV;
> +}
> +

Stupid question: Can we change the struct its_vlpi_map to contain a
vpe pointer or in stead of or in addition to the index?

Alternatively, can you look it up using
vcpu->arch.vgic_cpu.vgic_v3.its_vpe.irq() and another 'ioctl' in
irq_set_vcpu_affinity() somehow instead of looping around and testing?

> 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;
> - int ret;
> + int ret, idx;
>
> dump_routing(virq, irq_entry, true);
>
> @@ -280,6 +294,11 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
> if (ret)
> goto out;
>
> + idx = vgic_v4_vcpu_to_index(&kvm->arch.vgic.its_vm,
> + irq->target_vcpu);
> + if (idx < 0)
> + goto out;
> +
> /*
> * Emit the mapping request. If it fails, the ITS probably
> * isn't v4 compatible, so let's silently bail out. Holding
> @@ -290,7 +309,7 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
> .vm = &kvm->arch.vgic.its_vm,
> .vintid = irq->intid,
> .db_enabled = true,
> - .vpe_idx = irq->target_vcpu->vcpu_id,
> + .vpe_idx = idx,
> };
>
> if (its_map_vlpi(virq, &map))
>
> Another option would be to just pass the pointer to the vpe instead,
> and let the irq code to figure out the index, which can easily be
> derived the doorbells (vpe->vpe_db_lpi - vpe->its_vm->db_lpi_base).
>
> I'll work something out for the next version.

Ah, yeah, so I guess that is an option.

It should be pretty quick to loop over even hundreds of vcpus, but that
kind of thing just always seems wrong, somehow.

Thanks,
-Christoffer