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

Marc Zyngier
2017-08-30T12:51:24Z

On 30/08/17 12:46, Christoffer Dall wrote:
> 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?

This is obviously the right solution, because the *index* of the VPE
doesn't really matter for a map/unmap (it only matters for doorbell
operations, and that's a very different code path).

I came up with the following (untested, again), which is much more
appealing:

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index b47097a3e4b4..0607541fcafc 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -900,7 +900,7 @@ static void its_send_vmapti(struct its_device *dev, u32 id)
struct its_vlpi_map *map = &dev->event_map.vlpi_maps[id];
struct its_cmd_desc desc;

- desc.its_vmapti_cmd.vpe = map->vm->vpes[map->vpe_idx];
+ desc.its_vmapti_cmd.vpe = map->vpe;
desc.its_vmapti_cmd.dev = dev;
desc.its_vmapti_cmd.virt_id = map->vintid;
desc.its_vmapti_cmd.event_id = id;
@@ -914,7 +914,7 @@ static void its_send_vmovi(struct its_device *dev, u32 id)
struct its_vlpi_map *map = &dev->event_map.vlpi_maps[id];
struct its_cmd_desc desc;

- desc.its_vmovi_cmd.vpe = map->vm->vpes[map->vpe_idx];
+ desc.its_vmovi_cmd.vpe = map->vpe;
desc.its_vmovi_cmd.dev = dev;
desc.its_vmovi_cmd.event_id = id;
desc.its_vmovi_cmd.db_enabled = map->db_enabled;
diff --git a/include/linux/irqchip/arm-gic-v4.h b/include/linux/irqchip/arm-gic-v4.h
index 52661b838821..58a4d89aa82c 100644
--- a/include/linux/irqchip/arm-gic-v4.h
+++ b/include/linux/irqchip/arm-gic-v4.h
@@ -62,15 +62,15 @@ struct its_vpe {
* irq_set_vcpu_affinity().
*
* @vm: Pointer to the GICv4 notion of a VM
+ * @vpe: Pointer to the GICv4 notion of a virtual CPU (VPE)
* @vintid: Virtual LPI number
* @db_enabled: Is the VPE doorbell to be generated?
- * @vpe_idx: Index (0-based) of the VPE in this VM. Not the vpe_id!
*/
struct its_vlpi_map {
struct its_vm *vm;
+ struct its_vpe *vpe;
u32 vintid;
bool db_enabled;
- u16 vpe_idx;
};

enum its_vcpu_info_cmd_type {
diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index d790d0c74b8b..6ba3d73e0f70 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -715,7 +715,7 @@ static int vgic_its_cmd_handle_movi(struct kvm *kvm, struct vgic_its *its,
if (ret)
return ret;

- map.vpe_idx = vcpu->vcpu_id;
+ map.vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;

return its_map_vlpi(ite->irq->host_irq, &map);
}
@@ -1184,7 +1184,7 @@ static int vgic_its_cmd_handle_movall(struct kvm *kvm, struct vgic_its *its,
struct its_vlpi_map map;

if (!its_get_vlpi(irq->host_irq, &map)) {
- map.vpe_idx = vcpu2->vcpu_id;
+ map.vpe = &vcpu2->arch.vgic_cpu.vgic_v3.its_vpe;
its_map_vlpi(irq->host_irq, &map);
}
}
diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
index cf5d6e2de6b8..6ece88322013 100644
--- a/virt/kvm/arm/vgic/vgic-v4.c
+++ b/virt/kvm/arm/vgic/vgic-v4.c
@@ -288,9 +288,9 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
*/
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,
.db_enabled = true,
- .vpe_idx = irq->target_vcpu->vcpu_id,
};

if (its_map_vlpi(virq, &map))

Maybe I'll introduce a vcpu_to_vpe() helper, but it already looks much
better to me...

Thanks,

M.
--
Jazz is not dead. It just smells funny...