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KVM: x86/pmu: Reprogram mediated PMU event selectors on event filter updates

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Refresh the event selectors that are programmed into hardware when a PMC
is "reprogrammed" for a mediated PMU, i.e. if userspace changes the PMU
event filters

Note, KVM doesn't utilize the reprogramming infrastructure to handle
counter overflow for mediated PMUs, as there's no need to reprogram a
non-existent perf event.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Co-developed-by: Mingwei Zhang <mizhang@google.com>
Signed-off-by: Mingwei Zhang <mizhang@google.com>
[sean: add a helper to document behavior, split patch and rewrite changelog]
Tested-by: Xudong Hao <xudong.hao@intel.com>
Tested-by: Manali Shukla <manali.shukla@amd.com>
Link: https://patch.msgid.link/20251206001720.468579-26-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Dapeng Mi 2025-12-05 16:17:01 -08:00 committed by Sean Christopherson
parent 02918f0077
commit 3db871fe18
1 changed files with 24 additions and 0 deletions
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24
arch/x86/kvm/pmu.c
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@ -520,6 +520,25 @@ static bool pmc_is_event_allowed(struct kvm_pmc *pmc)
return is_fixed_event_allowed(filter, pmc->idx);
}
static void kvm_mediated_pmu_refresh_event_filter(struct kvm_pmc *pmc)
{
bool allowed = pmc_is_event_allowed(pmc);
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
if (pmc_is_gp(pmc)) {
pmc->eventsel_hw &= ~ARCH_PERFMON_EVENTSEL_ENABLE;
if (allowed)
pmc->eventsel_hw |= pmc->eventsel &
ARCH_PERFMON_EVENTSEL_ENABLE;
} else {
u64 mask = intel_fixed_bits_by_idx(pmc->idx - KVM_FIXED_PMC_BASE_IDX, 0xf);
pmu->fixed_ctr_ctrl_hw &= ~mask;
if (allowed)
pmu->fixed_ctr_ctrl_hw |= pmu->fixed_ctr_ctrl & mask;
}
}
static int reprogram_counter(struct kvm_pmc *pmc)
{
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
@ -528,6 +547,11 @@ static int reprogram_counter(struct kvm_pmc *pmc)
bool emulate_overflow;
u8 fixed_ctr_ctrl;
if (kvm_vcpu_has_mediated_pmu(pmu_to_vcpu(pmu))) {
kvm_mediated_pmu_refresh_event_filter(pmc);
return 0;
}
emulate_overflow = pmc_pause_counter(pmc);
if (!pmc_is_globally_enabled(pmc) || !pmc_is_locally_enabled(pmc) ||