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authorLike Xu <likexu@tencent.com>2022-04-09 09:52:26 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2022-04-21 13:16:14 -0400
commit75189d1de1b377e580ebd2d2c55914631eac9c64 (patch)
tree411e9a78ba15411a89c4529c6c7046aafa1bb4d1 /arch/x86/kvm/svm/pmu.c
parent0361bdfddca20c8855ea3bdbbbc9c999912b10ff (diff)
downloadlinux-75189d1de1b377e580ebd2d2c55914631eac9c64.tar.gz
KVM: x86/pmu: Update AMD PMC sample period to fix guest NMI-watchdog
NMI-watchdog is one of the favorite features of kernel developers, but it does not work in AMD guest even with vPMU enabled and worse, the system misrepresents this capability via /proc. This is a PMC emulation error. KVM does not pass the latest valid value to perf_event in time when guest NMI-watchdog is running, thus the perf_event corresponding to the watchdog counter will enter the old state at some point after the first guest NMI injection, forcing the hardware register PMC0 to be constantly written to 0x800000000001. Meanwhile, the running counter should accurately reflect its new value based on the latest coordinated pmc->counter (from vPMC's point of view) rather than the value written directly by the guest. Fixes: 168d918f2643 ("KVM: x86: Adjust counter sample period after a wrmsr") Reported-by: Dongli Cao <caodongli@kingsoft.com> Signed-off-by: Like Xu <likexu@tencent.com> Reviewed-by: Yanan Wang <wangyanan55@huawei.com> Tested-by: Yanan Wang <wangyanan55@huawei.com> Reviewed-by: Jim Mattson <jmattson@google.com> Message-Id: <20220409015226.38619-1-likexu@tencent.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/svm/pmu.c')
-rw-r--r--arch/x86/kvm/svm/pmu.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 24eb935b6f85..b14860863c39 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -257,6 +257,7 @@ static int amd_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
pmc = get_gp_pmc_amd(pmu, msr, PMU_TYPE_COUNTER);
if (pmc) {
pmc->counter += data - pmc_read_counter(pmc);
+ pmc_update_sample_period(pmc);
return 0;
}
/* MSR_EVNTSELn */