[PATCH] KVM: x86: Sync the pending Posted-Interrupts

From: Luwei Kang
Date: Fri Jan 18 2019 - 01:36:31 EST

Some Posted-Interrupts from passthrough devices may be lost or
overwritten when the vCPU is in runnable state.

The SN (Suppress Notification) of PID (Posted Interrupt Descriptor) will
be set when the vCPU is preempted (vCPU in KVM_MP_STATE_RUNNABLE state
but not running on physical CPU). If a posted interrupt coming at this
time, the irq remmaping facility will set the bit of PIR (Posted
Interrupt Requests) but ON (Outstanding Notification).
So this interrupt can't be sync to APIC virtualization register and
will not be handled by Guest because ON is zero.

Signed-off-by: Luwei Kang <luwei.kang@xxxxxxxxx>
arch/x86/kvm/vmx/vmx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f6915f1..820a03b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6048,7 +6048,7 @@ static int vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
bool max_irr_updated;

- if (pi_test_on(&vmx->pi_desc)) {
+ if (!bitmap_empty((unsigned long *)vmx->pi_desc.pir, NR_VECTORS)) {
* IOMMU can write to PIR.ON, so the barrier matters even on UP.