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authorMarc Zyngier <maz@kernel.org>2022-11-13 19:38:20 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-04-13 17:55:17 +0300
commit508d71a6770899facd26d4b92d9883656be67eaa (patch)
treef61108d2fd2a98d4dacec4e17300bf4a85864d09 /arch/arm64/kvm
parenteb3df961021b9c018cc609aa63aec9b3938e9fc3 (diff)
downloadlinux-508d71a6770899facd26d4b92d9883656be67eaa.tar.xz
KVM: arm64: PMU: Distinguish between 64bit counter and 64bit overflow
[ Upstream commit c82d28cbf1d4f9fe174041b4485c635cb970afa7 ] The PMU architecture makes a subtle difference between a 64bit counter and a counter that has a 64bit overflow. This is for example the case of the cycle counter, which can generate an overflow on a 32bit boundary if PMCR_EL0.LC==0 despite the accumulation being done on 64 bits. Use this distinction in the few cases where it matters in the code, as we will reuse this with PMUv3p5 long counters. Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20221113163832.3154370-5-maz@kernel.org Stable-dep-of: f6da81f650fa ("KVM: arm64: PMU: Don't save PMCR_EL0.{C,P} for the vCPU") Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'arch/arm64/kvm')
-rw-r--r--arch/arm64/kvm/pmu-emul.c43
1 files changed, 31 insertions, 12 deletions
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 57765be69bea..c146417b8178 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -51,13 +51,19 @@ 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);
+}
+
+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);
}
static bool kvm_pmu_counter_can_chain(struct kvm_vcpu *vcpu, u64 idx)
{
- return (!(idx & 1) && (idx + 1) < ARMV8_PMU_CYCLE_IDX);
+ return (!(idx & 1) && (idx + 1) < ARMV8_PMU_CYCLE_IDX &&
+ !kvm_pmu_idx_has_64bit_overflow(vcpu, idx));
}
static struct kvm_vcpu *kvm_pmc_to_vcpu(struct kvm_pmc *pmc)
@@ -97,7 +103,7 @@ u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx)
counter += perf_event_read_value(pmc->perf_event, &enabled,
&running);
- if (select_idx != ARMV8_PMU_CYCLE_IDX)
+ if (!kvm_pmu_idx_is_64bit(vcpu, select_idx))
counter = lower_32_bits(counter);
return counter;
@@ -423,6 +429,23 @@ static void kvm_pmu_counter_increment(struct kvm_vcpu *vcpu,
}
}
+/* Compute the sample period for a given counter value */
+static u64 compute_period(struct kvm_vcpu *vcpu, u64 select_idx, u64 counter)
+{
+ u64 val;
+
+ if (kvm_pmu_idx_is_64bit(vcpu, select_idx)) {
+ if (!kvm_pmu_idx_has_64bit_overflow(vcpu, select_idx))
+ val = -(counter & GENMASK(31, 0));
+ else
+ val = (-counter) & GENMASK(63, 0);
+ } else {
+ val = (-counter) & GENMASK(31, 0);
+ }
+
+ return val;
+}
+
/**
* When the perf event overflows, set the overflow status and inform the vcpu.
*/
@@ -442,10 +465,7 @@ static void kvm_pmu_perf_overflow(struct perf_event *perf_event,
* Reset the sample period to the architectural limit,
* i.e. the point where the counter overflows.
*/
- period = -(local64_read(&perf_event->count));
-
- if (!kvm_pmu_idx_is_64bit(vcpu, pmc->idx))
- period &= GENMASK(31, 0);
+ period = compute_period(vcpu, idx, local64_read(&perf_event->count));
local64_set(&perf_event->hw.period_left, 0);
perf_event->attr.sample_period = period;
@@ -571,14 +591,13 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx)
/*
* If counting with a 64bit counter, advertise it to the perf
- * code, carefully dealing with the initial sample period.
+ * code, carefully dealing with the initial sample period
+ * which also depends on the overflow.
*/
- if (kvm_pmu_idx_is_64bit(vcpu, select_idx)) {
+ if (kvm_pmu_idx_is_64bit(vcpu, select_idx))
attr.config1 |= PERF_ATTR_CFG1_COUNTER_64BIT;
- attr.sample_period = (-counter) & GENMASK(63, 0);
- } else {
- attr.sample_period = (-counter) & GENMASK(31, 0);
- }
+
+ attr.sample_period = compute_period(vcpu, select_idx, counter);
event = perf_event_create_kernel_counter(&attr, -1, current,
kvm_pmu_perf_overflow, pmc);