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KVM: x86: Snapshot the host's DEBUGCTL after disabling IRQs

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[ Upstream commit 189ecdb3e112da703ac0699f4ec76aa78122f911 ]

Snapshot the host's DEBUGCTL after disabling IRQs, as perf can toggle
debugctl bits from IRQ context, e.g. when enabling/disabling events via
smp_call_function_single().  Taking the snapshot (long) before IRQs are
disabled could result in KVM effectively clobbering DEBUGCTL due to using
a stale snapshot.

Cc: stable@vger.kernel.org
Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20250227222411.3490595-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Sean Christopherson
2025-08-14 17:25:27 -07:00
committed by Greg Kroah-Hartman
parent 76025761e8
commit a1d4091f94
1 changed files with 2 additions and 1 deletions
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3
arch/x86/kvm/x86.c
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@@ -4823,7 +4823,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
/* Save host pkru register if supported */
vcpu->arch.host_pkru = read_pkru();
vcpu->arch.host_debugctl = get_debugctlmsr();
/* Apply any externally detected TSC adjustments (due to suspend) */
if (unlikely(vcpu->arch.tsc_offset_adjustment)) {
@@ -10782,6 +10781,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
set_debugreg(0, 7);
}
vcpu->arch.host_debugctl = get_debugctlmsr();
guest_timing_enter_irqoff();
for (;;) {