Commit 1cf53587 authored Oct 10, 2017 by Paolo Bonzini

KVM: SVM: unconditionally wake up VCPU on IOMMU interrupt



Checking the mode is unnecessary, and is done without a memory barrier
separating the LAPIC write from the vcpu->mode read; in addition,
kvm_vcpu_wake_up is already doing a check for waiters on the wait queue
that has the same effect.

In practice it's safe because spin_lock has full-barrier semantics on x86,
but don't be too clever.

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent c1bd743e

arch/x86/kvm/svm.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -1034,15 +1034,12 @@ static int avic_ga_log_notifier(u32 ga_tag)
		}
		spin_unlock_irqrestore(&svm_vm_data_hash_lock, flags);

		if (!vcpu)
		return 0;

		/* Note:
		* At this point, the IOMMU should have already set the pending
		* bit in the vAPIC backing page. So, we just need to schedule
		* in the vcpu.
		*/
		if (vcpu->mode == OUTSIDE_GUEST_MODE)
		if (vcpu)
		kvm_vcpu_wake_up(vcpu);

		return 0;

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