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KVM: x86/pmu: Squash period for checkpointed events based on host HLE/RTM

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Zero out the sampling period for checkpointed events if the host supports
HLE or RTM, i.e. supports transactions and thus checkpointed events, not
based on whether the vCPU vendor model is Intel.  Perf's refusal to allow
a sample period for checkpointed events is based purely on whether or not
the CPU supports HLE/RTM transactions, i.e. perf has no knowledge of the
vCPU vendor model.

Note, it is _extremely_ unlikely that the existing code is a problem in
real world usage, as there are far, far bigger hurdles that would need to
be cleared to support cross-vendor vPMUs.  The motivation is mainly to
eliminate the use of guest_cpuid_is_intel(), in order to get to a state
where KVM pivots on AMD vs. Intel compatibility, i.e. doesn't check for
exactly vendor==Intel except in rare circumstances (i.e. for CPU quirks).

Cc: Like Xu <like.xu.linux@gmail.com>
Link: https://lore.kernel.org/r/20240405235603.1173076-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-04-05 16:55:56 -07:00
parent d5989a3533
commit 5a4f8b3026
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kvm/pmu.c
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@ -194,7 +194,7 @@ static int pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type, u64 config,
attr.sample_period = get_sample_period(pmc, pmc->counter);
if ((attr.config & HSW_IN_TX_CHECKPOINTED) &&
guest_cpuid_is_intel(pmc->vcpu)) {
(boot_cpu_has(X86_FEATURE_RTM) || boot_cpu_has(X86_FEATURE_HLE))) {
/*
* HSW_IN_TX_CHECKPOINTED is not supported with nonzero
* period. Just clear the sample period so at least