6.1-stable review patch. If anyone has any objections, please let me know.
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From: Mingwei Zhang mizhang@google.com
commit 05519c86d6997cfb9bb6c82ce1595d1015b718dc upstream.
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: 76d287b2342e ("KVM: x86/pmu: Drop "u8 ctrl, int idx" for reprogram_fixed_counter()") Cc: stable@vger.kernel.org Signed-off-by: Mingwei 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: Sean Christopherson seanjc@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/vmx/pmu_intel.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/kvm/vmx/pmu_intel.c +++ b/arch/x86/kvm/vmx/pmu_intel.c @@ -38,7 +38,7 @@ static int fixed_pmc_events[] = {1, 0, 7 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;