From: Haozhong Zhang <haozhong.zhang@intel.com>
Date: Mon, 18 Sep 2017 09:56:49 +0800
Subject: KVM: VMX: do not change SN bit in vmx_update_pi_irte()
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Git-commit: dc91f2eb1a4021eb6705c15e474942f84ab9b211
Patch-mainline: v4.14-rc2
References: bsc#1061017

In kvm_vcpu_trigger_posted_interrupt() and pi_pre_block(), KVM
assumes that PI notification events should not be suppressed when the
target vCPU is not blocked.

vmx_update_pi_irte() sets the SN field before changing an interrupt
from posting to remapping, but it does not check the vCPU mode.
Therefore, the change of SN field may break above the assumption.
Besides, I don't see reasons to suppress notification events here, so
remove the changes of SN field to avoid race condition.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Reported-by: "Ramamurthy, Venkatesh" <venkatesh.ramamurthy@intel.com>
Reported-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Fixes: 28b835d60fcc ("KVM: Update Posted-Interrupts Descriptor when vCPU is preempted")
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/kvm/vmx.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11440,12 +11440,8 @@ static int vmx_update_pi_irte(struct kvm
 
 		if (set)
 			ret = irq_set_vcpu_affinity(host_irq, &vcpu_info);
-		else {
-			/* suppress notification event before unposting */
-			pi_set_sn(vcpu_to_pi_desc(vcpu));
+		else
 			ret = irq_set_vcpu_affinity(host_irq, NULL);
-			pi_clear_sn(vcpu_to_pi_desc(vcpu));
-		}
 
 		if (ret < 0) {
 			printk(KERN_INFO "%s: failed to update PI IRTE\n",