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KVM: x86/pmu: Fix type length error when reading pmu->fixed_ctr_ctrl
commit05519c86d6
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:76d287b234
("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>
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@ -38,7 +38,7 @@ static int fixed_pmc_events[] = {1, 0, 7};
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static void reprogram_fixed_counters(struct kvm_pmu *pmu, u64 data)
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{
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struct kvm_pmc *pmc;
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u8 old_fixed_ctr_ctrl = pmu->fixed_ctr_ctrl;
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u64 old_fixed_ctr_ctrl = pmu->fixed_ctr_ctrl;
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int i;
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pmu->fixed_ctr_ctrl = data;
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