Patch "KVM: VMX: do not change SN bit in vmx_update_pi_irte()" has been added to the 4.9-stable tree

Patch "KVM: VMX: do not change SN bit in vmx_update_pi_irte()" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    KVM: VMX: do not change SN bit in vmx_update_pi_irte()

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-vmx-do-not-change-sn-bit-in-vmx_update_pi_irte.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From dc91f2eb1a4021eb6705c15e474942f84ab9b211 Mon Sep 17 00:00:00 2001
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()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Haozhong Zhang <haozhong.zhang@intel.com>

commit dc91f2eb1a4021eb6705c15e474942f84ab9b211 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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
@@ -11215,12 +11215,8 @@ 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",


Patches currently in stable-queue which might be from haozhong.zhang@intel.com are

queue-4.9/kvm-vmx-do-not-change-sn-bit-in-vmx_update_pi_irte.patch
queue-4.9/kvm-vmx-remove-warn_on_once-in-kvm_vcpu_trigger_posted_interrupt.patch