Commit 05519c86 authored by Mingwei Zhang's avatar Mingwei Zhang Committed by Sean Christopherson
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KVM: x86/pmu: Fix type length error when reading pmu->fixed_ctr_ctrl 



Use a u64 instead of a u8 when taking a snapshot of pmu->fixed_ctr_ctrl
when reprogramming fixed counters, as truncating the value results in KVM
thinking fixed counter 2 is already disabled (the bug also affects fixed
counters 3+, but KVM doesn't yet support those).  As a result, if the
guest disables fixed counter 2, KVM will get a false negative and fail to
reprogram/disable emulation of the counter, which can leads to incorrect
counts and spurious PMIs in the guest.

Fixes: 76d287b2 ("KVM: x86/pmu: Drop "u8 ctrl, int idx" for reprogram_fixed_counter()")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarMingwei Zhang <mizhang@google.com>
Link: https://lore.kernel.org/r/20240123221220.3911317-1-mizhang@google.com


[sean: rewrite changelog to call out the effects of the bug]
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 6231c9e1

arch/x86/kvm/vmx/pmu_intel.c

+1 −1
Original line number Diff line number Diff line
@@ -71,7 +71,7 @@ static int fixed_pmc_events[] = { 
static void reprogram_fixed_counters(struct kvm_pmu *pmu, u64 data)

{

	struct kvm_pmc *pmc;

	u8 old_fixed_ctr_ctrl = pmu->fixed_ctr_ctrl;

	u64 old_fixed_ctr_ctrl = pmu->fixed_ctr_ctrl;

	int i;



	pmu->fixed_ctr_ctrl = data;