Commit 2a140f3b authored Nov 29, 2017 by Radim Krčmář Committed by Paolo Bonzini Dec 14, 2017

KVM: x86: prevent MWAIT in guest with buggy MONITOR



The bug prevents MWAIT from waking up after a write to the monitored
cache line.
KVM might emulate a CPU model that shouldn't have the bug, so the guest
would not employ a workaround and possibly miss wakeups.
Better to avoid the situation.

Reviewed-by: Alexander Graf <agraf@suse.de>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent 0d37d26f

arch/x86/kvm/x86.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -281,6 +281,9 @@ static inline bool kvm_mwait_in_guest(void)
		return false;
		}

		if (boot_cpu_has_bug(X86_BUG_MONITOR))
		return false;

		/*
		* Intel CPUs without CPUID5_ECX_INTERRUPT_BREAK are problematic as
		* they would allow guest to stop the CPU completely by disabling

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