[PATCH v3 13/14] KVM: arm64: PMU: Implement PMUv3p5 long counter support

Marc Zyngier
2022-11-07T09:17:09Z

PMUv3p5 (which is mandatory with ARMv8.5) comes with some extra
features:

- All counters are 64bit

- The overflow point is controlled by the PMCR_EL0.LP bit

Add the required checks in the helpers that control counter
width and overflow, as well as the sysreg handling for the LP
bit. A new kvm_pmu_is_3p5() helper makes it easy to spot the
PMUv3p5 specific handling.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/pmu-emul.c | 8 +++++---
arch/arm64/kvm/sys_regs.c | 4 ++++
include/kvm/arm_pmu.h | 7 +++++++
3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index f126b45aa6c6..dc163e1a1fcf 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -52,13 +52,15 @@ static u32 kvm_pmu_event_mask(struct kvm *kvm)
*/
static bool kvm_pmu_idx_is_64bit(struct kvm_vcpu *vcpu, u64 select_idx)
{
- return (select_idx == ARMV8_PMU_CYCLE_IDX);
+ return (select_idx == ARMV8_PMU_CYCLE_IDX || kvm_pmu_is_3p5(vcpu));
}

static bool kvm_pmu_idx_has_64bit_overflow(struct kvm_vcpu *vcpu, u64 select_idx)
{
- return (select_idx == ARMV8_PMU_CYCLE_IDX &&
- __vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_LC);
+ u64 val = __vcpu_sys_reg(vcpu, PMCR_EL0);
+
+ return (select_idx < ARMV8_PMU_CYCLE_IDX && (val & ARMV8_PMU_PMCR_LP)) ||
+ (select_idx == ARMV8_PMU_CYCLE_IDX && (val & ARMV8_PMU_PMCR_LC));
}

static bool kvm_pmu_counter_can_chain(struct kvm_vcpu *vcpu, u64 idx)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 094b79b880a6..67633c939f38 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -654,6 +654,8 @@ static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
| (ARMV8_PMU_PMCR_MASK & 0xdecafbad)) & (~ARMV8_PMU_PMCR_E);
if (!kvm_supports_32bit_el0())
val |= ARMV8_PMU_PMCR_LC;
+ if (!kvm_pmu_is_3p5(vcpu))
+ val &= ~ARMV8_PMU_PMCR_LP;
__vcpu_sys_reg(vcpu, r->reg) = val;
}

@@ -703,6 +705,8 @@ static bool access_pmcr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
val |= p->regval & ARMV8_PMU_PMCR_MASK;
if (!kvm_supports_32bit_el0())
val |= ARMV8_PMU_PMCR_LC;
+ if (!kvm_pmu_is_3p5(vcpu))
+ val &= ~ARMV8_PMU_PMCR_LP;
__vcpu_sys_reg(vcpu, PMCR_EL0) = val;
kvm_pmu_handle_pmcr(vcpu, val);
kvm_vcpu_pmu_restore_guest(vcpu);
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 812f729c9108..3d526df9f3c5 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -89,6 +89,12 @@ void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
vcpu->arch.pmu.events = *kvm_get_pmu_events(); \
} while (0)

+/*
+ * Evaluates as true when emulating PMUv3p5, and false otherwise.
+ */
+#define kvm_pmu_is_3p5(vcpu) \
+ (vcpu->kvm->arch.dfr0_pmuver >= ID_AA64DFR0_EL1_PMUVer_V3P5)
+
u8 kvm_arm_pmu_get_pmuver_limit(void);

#else
@@ -153,6 +159,7 @@ static inline u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1)
}

#define kvm_vcpu_has_pmu(vcpu) ({ false; })
+#define kvm_pmu_is_3p5(vcpu) ({ false; })
static inline void kvm_pmu_update_vcpu_events(struct kvm_vcpu *vcpu) {}
static inline void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu) {}
static inline void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu) {}
--
2.34.1