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authorMarc Zyngier <maz@kernel.org>2019-10-03 20:02:08 +0300
committerMarc Zyngier <maz@kernel.org>2019-10-20 12:47:07 +0300
commitf4e23cf9477452640d2522f3286db5df6fcfe45a (patch)
tree3ba0f3b6e9dc1c02ec973ca96dabf3f068d32375
parentda0c9ea146cbe92b832f1b0f694840ea8eb33cce (diff)
downloadlinux-f4e23cf9477452640d2522f3286db5df6fcfe45a.tar.xz
KVM: arm64: pmu: Fix cycle counter truncation
When a counter is disabled, its value is sampled before the event is being disabled, and the value written back in the shadow register. In that process, the value gets truncated to 32bit, which is adequate for any counter but the cycle counter (defined as a 64bit counter). This obviously results in a corrupted counter, and things like "perf record -e cycles" not working at all when run in a guest... A similar, but less critical bug exists in kvm_pmu_get_counter_value. Make the truncation conditional on the counter not being the cycle counter, which results in a minor code reorganisation. Fixes: 80f393a23be6 ("KVM: arm/arm64: Support chained PMU counters") Reviewed-by: Andrew Murray <andrew.murray@arm.com> Reported-by: Julien Thierry <julien.thierry.kdev@gmail.com> Signed-off-by: Marc Zyngier <maz@kernel.org>
-rw-r--r--virt/kvm/arm/pmu.c22
1 files changed, 12 insertions, 10 deletions
diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c
index 362a01886bab..c30c3a74fc7f 100644
--- a/virt/kvm/arm/pmu.c
+++ b/virt/kvm/arm/pmu.c
@@ -146,8 +146,7 @@ u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
if (kvm_pmu_pmc_is_chained(pmc) &&
kvm_pmu_idx_is_high_counter(select_idx))
counter = upper_32_bits(counter);
-
- else if (!kvm_pmu_idx_is_64bit(vcpu, select_idx))
+ else if (select_idx != ARMV8_PMU_CYCLE_IDX)
counter = lower_32_bits(counter);
return counter;
@@ -193,7 +192,7 @@ static void kvm_pmu_release_perf_event(struct kvm_pmc *pmc)
*/
static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc)
{
- u64 counter, reg;
+ u64 counter, reg, val;
pmc = kvm_pmu_get_canonical_pmc(pmc);
if (!pmc->perf_event)
@@ -201,16 +200,19 @@ static void kvm_pmu_stop_counter(struct kvm_vcpu *vcpu, struct kvm_pmc *pmc)
counter = kvm_pmu_get_pair_counter_value(vcpu, pmc);
- if (kvm_pmu_pmc_is_chained(pmc)) {
- reg = PMEVCNTR0_EL0 + pmc->idx;
- __vcpu_sys_reg(vcpu, reg) = lower_32_bits(counter);
- __vcpu_sys_reg(vcpu, reg + 1) = upper_32_bits(counter);
+ if (pmc->idx == ARMV8_PMU_CYCLE_IDX) {
+ reg = PMCCNTR_EL0;
+ val = counter;
} else {
- reg = (pmc->idx == ARMV8_PMU_CYCLE_IDX)
- ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + pmc->idx;
- __vcpu_sys_reg(vcpu, reg) = lower_32_bits(counter);
+ reg = PMEVCNTR0_EL0 + pmc->idx;
+ val = lower_32_bits(counter);
}
+ __vcpu_sys_reg(vcpu, reg) = val;
+
+ if (kvm_pmu_pmc_is_chained(pmc))
+ __vcpu_sys_reg(vcpu, reg + 1) = upper_32_bits(counter);
+
kvm_pmu_release_perf_event(pmc);
}