From 2924b52117b2812e9633d5ea337333299166d373 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 20 May 2019 17:34:30 +0200
Subject: [PATCH] KVM: x86/pmu: do not mask the value that is written to fixed
PMUs
According to the SDM, for MSR_IA32_PERFCTR0/1 "the lower-order 32 bits of
each MSR may be written with any value, and the high-order 8 bits are
sign-extended according to the value of bit 31", but the fixed counters
in real hardware are limited to the width of the fixed counters ("bits
beyond the width of the fixed-function counter are reserved and must be
written as zeros"). Fix KVM to do the same.
Reported-by: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/vmx/pmu_intel.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index b6f5157445fe8..a99613a060dd8 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -240,11 +240,14 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
}
break;
default:
- if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
- (pmc = get_fixed_pmc(pmu, msr))) {
- if (!msr_info->host_initiated)
- data = (s64)(s32)data;
- pmc->counter += data - pmc_read_counter(pmc);
+ if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0))) {
+ if (msr_info->host_initiated)
+ pmc->counter = data;
+ else
+ pmc->counter = (s32)data;
+ return 0;
+ } else if ((pmc = get_fixed_pmc(pmu, msr))) {
+ pmc->counter = data;
return 0;
} else if ((pmc = get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0))) {
if (data == pmc->eventsel)
--
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