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

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>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1b8b1a1bf7e94764c563e5974c1352a5e191c1f9..ce8c2aa46ec20d7098782feaa36c46142af39b05 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11604,12 +11604,8 @@ static int vmx_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
 
                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",