[PATCH v2 1/5] KVM: nVMX: Remove pi_pending as signal to process nested posted-interrupts

[Liran Alon <liran.alon@xxxxxxxxxx>]

When L1 wants to send a posted-interrupt to another L1 CPU which runs
L2, it does the following operations:
1. Sets the relevant bit in vmx->nested.pi_desc PIR.
2. Set ON bit in vmx->nested.pi_desc->control field.
3. Sends an IPI to dest L1 CPU by writing the the posted-interrupt
   notification-vector into the LAPIC ICR.

Step (3) will exit to L0 on APIC_WRITE which will eventually reach
vmx_deliver_nested_posted_interrupt(). If dest L0 CPU is in guest,
then a physical IPI of notification-vector will be sent which will
trigger evaluation of posted-interrupts and clear
vmx->nested.pi_desc->control ON bit.
Otherwise (or if dest L0 CPU exited from guest just before sending the
physical IPI), the nested-posted-interrupts will be evaluated on next
vmentry by vmx_complete_nested_posted_interrupt().

In order for vmx_complete_nested_posted_interrupt() to know if it
should do any work, the flag vmx->nested.pi_pending was used which
was set by vmx_deliver_nested_posted_interrupt().

However, this seems unnecessary because if posted-interrupts was not
processed yet, vmx->nested.pi_desc->control ON bit should still be
set. Therefore, it should suffice to use it in order to know if work
should be done.

Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/kvm/vmx.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 714a0673ec3c..f5074ec5701b 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -453,7 +453,6 @@ struct nested_vmx {
 	struct page *virtual_apic_page;
 	struct page *pi_desc_page;
 	struct pi_desc *pi_desc;
-	bool pi_pending;
 	u16 posted_intr_nv;
 
 	unsigned long *msr_bitmap;
@@ -5050,10 +5049,9 @@ static void vmx_complete_nested_posted_interrupt(struct kvm_vcpu *vcpu)
 	void *vapic_page;
 	u16 status;
 
-	if (!vmx->nested.pi_desc || !vmx->nested.pi_pending)
+	if (!vmx->nested.pi_desc)
 		return;
 
-	vmx->nested.pi_pending = false;
 	if (!pi_test_and_clear_on(vmx->nested.pi_desc))
 		return;
 
@@ -5126,7 +5124,6 @@ static int vmx_deliver_nested_posted_interrupt(struct kvm_vcpu *vcpu,
 		 * If a posted intr is not recognized by hardware,
 		 * we will accomplish it in the next vmentry.
 		 */
-		vmx->nested.pi_pending = true;
 		kvm_make_request(KVM_REQ_EVENT, vcpu);
 		return 0;
 	}
@@ -10488,7 +10485,6 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	/* Posted interrupts setting is only taken from vmcs12.  */
 	if (nested_cpu_has_posted_intr(vmcs12)) {
 		vmx->nested.posted_intr_nv = vmcs12->posted_intr_nv;
-		vmx->nested.pi_pending = false;
 		vmcs_write16(POSTED_INTR_NV, POSTED_INTR_NESTED_VECTOR);
 	} else {
 		exec_control &= ~PIN_BASED_POSTED_INTR;
-- 
1.9.1