[PATCH v5 27/36] KVM: arm64: gic-v5: Mandate architected PPI for PMU emulation on GICv5

Sascha Bischoff
2026-02-26T16:03:36Z

Make it mandatory to use the architected PPI when running a GICv5
guest. Attempts to set anything other than the architected PPI (23)
are rejected.

Additionally, KVM_ARM_VCPU_PMU_V3_INIT is relaxed to no longer require
KVM_ARM_VCPU_PMU_V3_IRQ to be called for GICv5-based guests. In this
case, the architectued PPI is automatically used.

Documentation is bumped accordingly.

Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
---
Documentation/virt/kvm/devices/vcpu.rst | 5 +++--
arch/arm64/kvm/pmu-emul.c | 13 +++++++++++--
include/kvm/arm_pmu.h | 5 ++++-
3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt/kvm/devices/vcpu.rst
index 60bf205cb3730..5e38058200105 100644
--- a/Documentation/virt/kvm/devices/vcpu.rst
+++ b/Documentation/virt/kvm/devices/vcpu.rst
@@ -37,7 +37,8 @@ Returns:
A value describing the PMUv3 (Performance Monitor Unit v3) overflow interrupt
number for this vcpu. This interrupt could be a PPI or SPI, but the interrupt
type must be same for each vcpu. As a PPI, the interrupt number is the same for
-all vcpus, while as an SPI it must be a separate number per vcpu.
+all vcpus, while as an SPI it must be a separate number per vcpu. For
+GICv5-based guests, the architected PPI (23) must be used.

1.2 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_INIT
---------------------------------------
@@ -50,7 +51,7 @@ Returns:
-EEXIST Interrupt number already used
-ENODEV PMUv3 not supported or GIC not initialized
-ENXIO PMUv3 not supported, missing VCPU feature or interrupt
- number not set
+ number not set (non-GICv5 guests, only)
-EBUSY PMUv3 already initialized
======= ======================================================

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 41a3c5dc2bcac..e1860acae641f 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -962,8 +962,13 @@ static int kvm_arm_pmu_v3_init(struct kvm_vcpu *vcpu)
if (!vgic_initialized(vcpu->kvm))
return -ENODEV;

- if (!kvm_arm_pmu_irq_initialized(vcpu))
- return -ENXIO;
+ if (!kvm_arm_pmu_irq_initialized(vcpu)) {
+ if (!vgic_is_v5(vcpu->kvm))
+ return -ENXIO;
+
+ /* Use the architected irq number for GICv5. */
+ vcpu->arch.pmu.irq_num = KVM_ARMV8_PMU_GICV5_IRQ;
+ }

ret = kvm_vgic_set_owner(vcpu, vcpu->arch.pmu.irq_num,
&vcpu->arch.pmu);
@@ -988,6 +993,10 @@ static bool pmu_irq_is_valid(struct kvm *kvm, int irq)
unsigned long i;
struct kvm_vcpu *vcpu;

+ /* On GICv5, the PMUIRQ is architecturally mandated to be PPI 23 */
+ if (vgic_is_v5(kvm) && irq != KVM_ARMV8_PMU_GICV5_IRQ)
+ return false;
+
kvm_for_each_vcpu(i, vcpu, kvm) {
if (!kvm_arm_pmu_irq_initialized(vcpu))
continue;
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 96754b51b4116..0a36a3d5c8944 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -12,6 +12,9 @@

#define KVM_ARMV8_PMU_MAX_COUNTERS 32

+/* PPI #23 - architecturally specified for GICv5 */
+#define KVM_ARMV8_PMU_GICV5_IRQ 0x20000017
+
#if IS_ENABLED(CONFIG_HW_PERF_EVENTS) && IS_ENABLED(CONFIG_KVM)
struct kvm_pmc {
u8 idx; /* index into the pmu->pmc array */
@@ -38,7 +41,7 @@ struct arm_pmu_entry {
};

bool kvm_supports_guest_pmuv3(void);
-#define kvm_arm_pmu_irq_initialized(v) ((v)->arch.pmu.irq_num >= VGIC_NR_SGIS)
+#define kvm_arm_pmu_irq_initialized(v) ((v)->arch.pmu.irq_num != 0)
u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx);
void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val);
void kvm_pmu_set_counter_value_user(struct kvm_vcpu *vcpu, u64 select_idx, u64 val);
--
2.34.1