From: Paolo Bonzini <pbonzini@redhat.com>
Date: Tue, 10 Oct 2017 10:51:56 +0000 (+0200)
Subject: KVM: SVM: unconditionally wake up VCPU on IOMMU interrupt
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=1cf53587c03025885af359da3bd0be091aa34b53;p=openwrt%2Fstaging%2Fblogic.git

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>
---

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 0e68f0b3cbf7..3e4337ee59cb 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -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;