[PATCH v3 59/62] KVM: SVM: Consolidate IRTE update when toggling AVIC on/off

Sean Christopherson
2025-06-11T22:48:38Z

Fold the IRTE modification logic in avic_refresh_apicv_exec_ctrl() into
__avic_vcpu_{load,put}(), and add a param to the helpers to communicate
whether or not AVIC is being toggled, i.e. if IRTE needs a "full" update,
or just a quick update to set the CPU and IsRun.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/svm/avic.c | 85 ++++++++++++++++++++++-------------------
1 file changed, 46 insertions(+), 39 deletions(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 1e6e5d1f6b4e..2e47559a4134 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -810,7 +810,28 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
return irq_set_vcpu_affinity(host_irq, NULL);
}

-static void avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu)
+enum avic_vcpu_action {
+ /*
+ * There is no need to differentiate between activate and deactivate,
+ * as KVM only refreshes AVIC state when the vCPU is scheduled in and
+ * isn't blocking, i.e. the pCPU must always be (in)valid when AVIC is
+ * being (de)activated.
+ */
+ AVIC_TOGGLE_ON_OFF = BIT(0),
+ AVIC_ACTIVATE = AVIC_TOGGLE_ON_OFF,
+ AVIC_DEACTIVATE = AVIC_TOGGLE_ON_OFF,
+
+ /*
+ * No unique action is required to deal with a vCPU that stops/starts
+ * running, as IRTEs are configured to generate GALog interrupts at all
+ * times.
+ */
+ AVIC_START_RUNNING = 0,
+ AVIC_STOP_RUNNING = 0,
+};
+
+static void avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu,
+ enum avic_vcpu_action action)
{
struct vcpu_svm *svm = to_svm(vcpu);
struct kvm_kernel_irqfd *irqfd;
@@ -824,11 +845,20 @@ static void avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu)
if (list_empty(&svm->ir_list))
return;

- list_for_each_entry(irqfd, &svm->ir_list, vcpu_list)
- WARN_ON_ONCE(amd_iommu_update_ga(cpu, irqfd->irq_bypass_data));
+ list_for_each_entry(irqfd, &svm->ir_list, vcpu_list) {
+ void *data = irqfd->irq_bypass_data;
+
+ if (!(action & AVIC_TOGGLE_ON_OFF))
+ WARN_ON_ONCE(amd_iommu_update_ga(cpu, data));
+ else if (cpu >= 0)
+ WARN_ON_ONCE(amd_iommu_activate_guest_mode(data, cpu));
+ else
+ WARN_ON_ONCE(amd_iommu_deactivate_guest_mode(data));
+ }
}

-static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu,
+ enum avic_vcpu_action action)
{
struct kvm_svm *kvm_svm = to_kvm_svm(vcpu->kvm);
int h_physical_id = kvm_cpu_get_apicid(cpu);
@@ -873,7 +903,7 @@ static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)

WRITE_ONCE(kvm_svm->avic_physical_id_table[vcpu->vcpu_id], entry);

- avic_update_iommu_vcpu_affinity(vcpu, h_physical_id);
+ avic_update_iommu_vcpu_affinity(vcpu, h_physical_id, action);

spin_unlock_irqrestore(&svm->ir_list_lock, flags);
}
@@ -890,10 +920,10 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
if (kvm_vcpu_is_blocking(vcpu))
return;

- __avic_vcpu_load(vcpu, cpu);
+ __avic_vcpu_load(vcpu, cpu, AVIC_START_RUNNING);
}

-static void __avic_vcpu_put(struct kvm_vcpu *vcpu)
+static void __avic_vcpu_put(struct kvm_vcpu *vcpu, enum avic_vcpu_action action)
{
struct kvm_svm *kvm_svm = to_kvm_svm(vcpu->kvm);
struct vcpu_svm *svm = to_svm(vcpu);
@@ -915,7 +945,7 @@ static void __avic_vcpu_put(struct kvm_vcpu *vcpu)
*/
spin_lock_irqsave(&svm->ir_list_lock, flags);

- avic_update_iommu_vcpu_affinity(vcpu, -1);
+ avic_update_iommu_vcpu_affinity(vcpu, -1, action);

entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK;
svm->avic_physical_id_entry = entry;
@@ -941,7 +971,7 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu)
if (!(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK))
return;

- __avic_vcpu_put(vcpu);
+ __avic_vcpu_put(vcpu, AVIC_STOP_RUNNING);
}

void avic_refresh_virtual_apic_mode(struct kvm_vcpu *vcpu)
@@ -970,41 +1000,18 @@ void avic_refresh_virtual_apic_mode(struct kvm_vcpu *vcpu)

void avic_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
{
- bool activated = kvm_vcpu_apicv_active(vcpu);
- int apic_id = kvm_cpu_get_apicid(vcpu->cpu);
- struct vcpu_svm *svm = to_svm(vcpu);
- struct kvm_kernel_irqfd *irqfd;
- unsigned long flags;
-
if (!enable_apicv)
return;

+ /* APICv should only be toggled on/off while the vCPU is running. */
+ WARN_ON_ONCE(kvm_vcpu_is_blocking(vcpu));
+
avic_refresh_virtual_apic_mode(vcpu);

- if (activated)
- __avic_vcpu_load(vcpu, vcpu->cpu);
+ if (kvm_vcpu_apicv_active(vcpu))
+ __avic_vcpu_load(vcpu, vcpu->cpu, AVIC_ACTIVATE);
else
- __avic_vcpu_put(vcpu);
-
- /*
- * Here, we go through the per-vcpu ir_list to update all existing
- * interrupt remapping table entry targeting this vcpu.
- */
- spin_lock_irqsave(&svm->ir_list_lock, flags);
-
- if (list_empty(&svm->ir_list))
- goto out;
-
- list_for_each_entry(irqfd, &svm->ir_list, vcpu_list) {
- void *data = irqfd->irq_bypass_data;
-
- if (activated)
- WARN_ON_ONCE(amd_iommu_activate_guest_mode(data, apic_id));
- else
- WARN_ON_ONCE(amd_iommu_deactivate_guest_mode(data));
- }
-out:
- spin_unlock_irqrestore(&svm->ir_list_lock, flags);
+ __avic_vcpu_put(vcpu, AVIC_DEACTIVATE);
}

void avic_vcpu_blocking(struct kvm_vcpu *vcpu)
@@ -1030,7 +1037,7 @@ void avic_vcpu_blocking(struct kvm_vcpu *vcpu)
* CPU and cause noisy neighbor problems if the VM is sending interrupts
* to the vCPU while it's scheduled out.
*/
- avic_vcpu_put(vcpu);
+ __avic_vcpu_put(vcpu, AVIC_STOP_RUNNING);
}

void avic_vcpu_unblocking(struct kvm_vcpu *vcpu)
--
2.50.0.rc1.591.g9c95f17f64-goog