[PATCH v3 19/22] perf: arm_pmuv3: Handle IRQs for Partitioned PMU guest counters

Colton Lewis
2025-06-26T20:06:13Z

Guest counters will still trigger interrupts that need to be handled
by the host PMU interrupt handler. Clear the overflow flags in
hardware to handle the interrupt as normal, but record which guest
overflow flags were set in the virtual overflow register for later
injecting the interrupt into the guest.

Signed-off-by: Colton Lewis <coltonlewis@google.com>
---
arch/arm/include/asm/arm_pmuv3.h | 6 ++++++
arch/arm64/include/asm/kvm_pmu.h | 2 ++
arch/arm64/kvm/pmu-part.c | 17 +++++++++++++++++
drivers/perf/arm_pmuv3.c | 9 +++++++++
4 files changed, 34 insertions(+)

diff --git a/arch/arm/include/asm/arm_pmuv3.h b/arch/arm/include/asm/arm_pmuv3.h
index 5f6269039f44..36638efe4258 100644
--- a/arch/arm/include/asm/arm_pmuv3.h
+++ b/arch/arm/include/asm/arm_pmuv3.h
@@ -180,6 +180,11 @@ static inline void write_pmintenset(u32 val)
write_sysreg(val, PMINTENSET);
}

+static inline u32 read_pmintenset(void)
+{
+ return read_sysreg(PMINTENSET);
+}
+
static inline void write_pmintenclr(u32 val)
{
write_sysreg(val, PMINTENCLR);
@@ -249,6 +254,7 @@ static inline u64 kvm_pmu_guest_counter_mask(struct arm_pmu *pmu)
return ~0;
}

+static inline void kvm_pmu_handle_guest_irq(u64 govf) {}

static inline bool has_vhe(void)
{
diff --git a/arch/arm64/include/asm/kvm_pmu.h b/arch/arm64/include/asm/kvm_pmu.h
index 4f0741bf6779..03e3bd318e4b 100644
--- a/arch/arm64/include/asm/kvm_pmu.h
+++ b/arch/arm64/include/asm/kvm_pmu.h
@@ -95,6 +95,7 @@ u64 kvm_pmu_host_counter_mask(struct arm_pmu *pmu);
u64 kvm_pmu_guest_counter_mask(struct arm_pmu *pmu);
void kvm_pmu_host_counters_enable(void);
void kvm_pmu_host_counters_disable(void);
+void kvm_pmu_handle_guest_irq(u64 govf);

u8 kvm_pmu_guest_num_counters(struct kvm_vcpu *vcpu);
u8 kvm_pmu_hpmn(struct kvm_vcpu *vcpu);
@@ -291,6 +292,7 @@ static inline u64 kvm_pmu_guest_counter_mask(struct arm_pmu *pmu)

static inline void kvm_pmu_host_counters_enable(void) {}
static inline void kvm_pmu_host_counters_disable(void) {}
+static inline void kvm_pmu_handle_guest_irq(u64 govf) {}

#endif

diff --git a/arch/arm64/kvm/pmu-part.c b/arch/arm64/kvm/pmu-part.c
index 1451870757e1..bd04c37b19b9 100644
--- a/arch/arm64/kvm/pmu-part.c
+++ b/arch/arm64/kvm/pmu-part.c
@@ -338,3 +338,20 @@ void kvm_pmu_put(struct kvm_vcpu *vcpu)
val = read_pmintenset();
__vcpu_assign_sys_reg(vcpu, PMINTENSET_EL1, val & mask);
}
+
+/**
+ * kvm_pmu_handle_guest_irq() - Record IRQs in guest counters
+ * @govf: Bitmask of guest overflowed counters
+ *
+ * Record IRQs from overflows in guest-reserved counters in the VCPU
+ * register for the guest to clear later.
+ */
+void kvm_pmu_handle_guest_irq(u64 govf)
+{
+ struct kvm_vcpu *vcpu = kvm_get_running_vcpu();
+
+ if (!vcpu)
+ return;
+
+ __vcpu_rmw_sys_reg(vcpu, PMOVSSET_EL0, |=, govf);
+}
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index 5836672a3dd9..dba7dcee8258 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -750,6 +750,8 @@ static u64 armv8pmu_getreset_flags(void)

/* Write to clear flags */
value &= ARMV8_PMU_CNT_MASK_ALL;
+ /* Only reset interrupt enabled counters. */
+ value &= read_pmintenset();
write_pmovsclr(value);

return value;
@@ -852,6 +854,7 @@ static void armv8pmu_stop(struct arm_pmu *cpu_pmu)
static irqreturn_t armv8pmu_handle_irq(struct arm_pmu *cpu_pmu)
{
u64 pmovsr;
+ u64 govf;
struct perf_sample_data data;
struct pmu_hw_events *cpuc = this_cpu_ptr(cpu_pmu->hw_events);
struct pt_regs *regs;
@@ -906,6 +909,12 @@ static irqreturn_t armv8pmu_handle_irq(struct arm_pmu *cpu_pmu)
*/
perf_event_overflow(event, &data, regs);
}
+
+ govf = pmovsr & kvm_pmu_guest_counter_mask(cpu_pmu);
+
+ if (kvm_pmu_is_partitioned(cpu_pmu) && govf)
+ kvm_pmu_handle_guest_irq(govf);
+
armv8pmu_start(cpu_pmu);

return IRQ_HANDLED;
--
2.50.0.727.gbf7dc18ff4-goog