KVM: x86: do not scan IRR twice on APICv vmentry

Calls to apic_find_highest_irr are scanning IRR twice, once
in vmx_sync_pir_from_irr and once in apic_search_irr.  Change
sync_pir_from_irr to get the new maximum IRR from kvm_apic_update_irr;
now that it does the computation, it can also do the RVI write.

In order to avoid complications in svm.c, make the callback optional.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 19 insertions, 12 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4ac9b484e244..d03cb62b70d2 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6649,8 +6649,10 @@ static __init int hardware_setup(void)
 	if (!cpu_has_vmx_ple())
 		ple_gap = 0;
 
-	if (!cpu_has_vmx_apicv())
+	if (!cpu_has_vmx_apicv()) {
 		enable_apicv = 0;
+		kvm_x86_ops->sync_pir_to_irr = NULL;
+	}
 
 	if (cpu_has_vmx_tsc_scaling()) {
 		kvm_has_tsc_control = true;
@@ -8722,20 +8724,25 @@ static void vmx_hwapic_irr_update(struct kvm_vcpu *vcpu, int max_irr)
 	}
 }
 
-static void vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
+static int vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	int max_irr;
 
-	if (!pi_test_on(&vmx->pi_desc))
-		return;
-
-	pi_clear_on(&vmx->pi_desc);
-	/*
-	 * IOMMU can write to PIR.ON, so the barrier matters even on UP.
-	 * But on x86 this is just a compiler barrier anyway.
-	 */
-	smp_mb__after_atomic();
-	kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
+	WARN_ON(!vcpu->arch.apicv_active);
+	if (pi_test_on(&vmx->pi_desc)) {
+		pi_clear_on(&vmx->pi_desc);
+		/*
+		 * IOMMU can write to PIR.ON, so the barrier matters even on UP.
+		 * But on x86 this is just a compiler barrier anyway.
+		 */
+		smp_mb__after_atomic();
+		max_irr = kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
+	} else {
+		max_irr = kvm_lapic_find_highest_irr(vcpu);
+	}
+	vmx_hwapic_irr_update(vcpu, max_irr);
+	return max_irr;
 }
 
 static void vmx_load_eoi_exitmap(struct kvm_vcpu *vcpu, u64 *eoi_exit_bitmap)