diff mbox series

[v2,1/5] KVM: x86/pmu: Prevent the PMU from counting disallowed events

Message ID 20230228000644.3204402-2-aaronlewis@google.com (mailing list archive)
State New, archived
Headers show
Series Fix "Instructions Retired" from incorrectly counting | expand

Commit Message

Aaron Lewis Feb. 28, 2023, 12:06 a.m. UTC 
When counting "Instructions Retired" (0xc0) in a guest, KVM will
occasionally increment the PMU counter regardless of if that event is
being filtered. This is because some PMU events are incremented via
kvm_pmu_trigger_event(), which doesn't know about the event filter. Add
the event filter to kvm_pmu_trigger_event(), so events that are
disallowed do not increment their counters.

Fixes: 9cd803d496e7 ("KVM: x86: Update vPMCs when retiring instructions")
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
---
 arch/x86/kvm/pmu.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

Comments

Like Xu March 3, 2023, 5:55 a.m. UTC | #1 
On 28/2/2023 8:06 am, Aaron Lewis wrote:
> +static bool pmc_is_allowed(struct kvm_pmc *pmc)

This function name is a little less self-expressive since a programmable PMC
is likely available if the counter is accessible.

How about rename it to event_is_allowed(..) or pmc_cur_event_is_allowed(..) ?

> +{
> +	return pmc_is_enabled(pmc) && pmc_speculative_in_use(pmc) &&
> +	       check_pmu_event_filter(pmc);
> +}
diff mbox series

Patch

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 612e6c70ce2e..0fe23bda855b 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -400,6 +400,12 @@  static bool check_pmu_event_filter(struct kvm_pmc *pmc)
 	return is_fixed_event_allowed(filter, pmc->idx);
 }
 
+static bool pmc_is_allowed(struct kvm_pmc *pmc)
+{
+	return pmc_is_enabled(pmc) && pmc_speculative_in_use(pmc) &&
+	       check_pmu_event_filter(pmc);
+}
+
 static void reprogram_counter(struct kvm_pmc *pmc)
 {
 	struct kvm_pmu *pmu = pmc_to_pmu(pmc);
@@ -409,10 +415,7 @@  static void reprogram_counter(struct kvm_pmc *pmc)
 
 	pmc_pause_counter(pmc);
 
-	if (!pmc_speculative_in_use(pmc) || !pmc_is_enabled(pmc))
-		goto reprogram_complete;
-
-	if (!check_pmu_event_filter(pmc))
+	if (!pmc_is_allowed(pmc))
 		goto reprogram_complete;
 
 	if (pmc->counter < pmc->prev_counter)
@@ -684,7 +687,7 @@  void kvm_pmu_trigger_event(struct kvm_vcpu *vcpu, u64 perf_hw_id)
 	for_each_set_bit(i, pmu->all_valid_pmc_idx, X86_PMC_IDX_MAX) {
 		pmc = static_call(kvm_x86_pmu_pmc_idx_to_pmc)(pmu, i);
 
-		if (!pmc || !pmc_is_enabled(pmc) || !pmc_speculative_in_use(pmc))
+		if (!pmc || !pmc_is_allowed(pmc))
 			continue;
 
 		/* Ignore checks for edge detect, pin control, invert and CMASK bits */