On Mon, Sep 11, 2023, Mingwei Zhang wrote:
> Use atomic bit operations for pmu->global_status because it may suffer from
> race conditions between emulated overflow in KVM vPMU and PEBS overflow in
> host PMI handler.
Only if the host PMI occurs on a different pCPU, and if that can happen don't we
have a much larger problem?
> Fixes: f331601c65ad ("KVM: x86/pmu: Don't generate PEBS records for emulated instructions")
> Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
> ---
> arch/x86/kvm/pmu.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
> index edb89b51b383..00b48f25afdb 100644
> --- a/arch/x86/kvm/pmu.c
> +++ b/arch/x86/kvm/pmu.c
> @@ -117,11 +117,11 @@ static inline void __kvm_perf_overflow(struct kvm_pmc *pmc, bool in_pmi)
> skip_pmi = true;
> } else {
> /* Indicate PEBS overflow PMI to guest. */
> - skip_pmi = __test_and_set_bit(GLOBAL_STATUS_BUFFER_OVF_BIT,
> - (unsigned long *)&pmu->global_status);
> + skip_pmi = test_and_set_bit(GLOBAL_STATUS_BUFFER_OVF_BIT,
> + (unsigned long *)&pmu->global_status);
> }
> } else {
> - __set_bit(pmc->idx, (unsigned long *)&pmu->global_status);
> + set_bit(pmc->idx, (unsigned long *)&pmu->global_status);
> }
>
> if (!pmc->intr || skip_pmi)
>
> base-commit: e2013f46ee2e721567783557c301e5c91d0b74ff
> --
> 2.42.0.283.g2d96d420d3-goog
>
