From: Paolo Bonzini <pbonzini@redhat.com>
Date: Tue, 10 Oct 2017 12:51:56 +0200
Subject: KVM: SVM: unconditionally wake up VCPU on IOMMU interrupt
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Patch-mainline: v4.15-rc1
Git-commit: 1cf53587c03025885af359da3bd0be091aa34b53
References: bsc#1077761

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>
Acked-by: Alexander Graf <agraf@suse.de>
---
 arch/x86/kvm/svm.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1033,15 +1033,12 @@
 	}
 	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;