KVM: x86: check PIR even for vCPUs with disabled APICv

The IRTE for an assigned device can trigger a POSTED_INTR_VECTOR even
if APICv is disabled on the vCPU that receives it.  In that case, the
interrupt will just cause a vmexit and leave the ON bit set together
with the PIR bit corresponding to the interrupt.

Right now, the interrupt would not be delivered until APICv is re-enabled.
However, fixing this is just a matter of always doing the PIR->IRR
synchronization, even if the vCPU has temporarily disabled APICv.

This is not a problem for performance, or if anything it is an
improvement.  First, in the common case where vcpu->arch.apicv_active is
true, one fewer check has to be performed.  Second, static_call_cond will
elide the function call if APICv is not present or disabled.  Finally,
in the case for AMD hardware we can remove the sync_pir_to_irr callback:
it is only needed for apic_has_interrupt_for_ppr, and that function
already has a fallback for !APICv.

Cc: stable@vger.kernel.org
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Message-Id: <20211123004311.2954158-4-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 759952dd122284b183c3735bad40717495920304..f206fc35deff6ef4d0a236eddd4476635d4e5b1f 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -707,7 +707,7 @@ static void pv_eoi_clr_pending(struct kvm_vcpu *vcpu)
 static int apic_has_interrupt_for_ppr(struct kvm_lapic *apic, u32 ppr)
 {
        int highest_irr;
-       if (apic->vcpu->arch.apicv_active)
+       if (kvm_x86_ops.sync_pir_to_irr)
                highest_irr = static_call(kvm_x86_sync_pir_to_irr)(apic->vcpu);
        else
                highest_irr = apic_find_highest_irr(apic);

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 5630c241d5f6e0bdf1899163cfdfef57c18b5d47..d0f68d11ec70bec31890e1dbd23b5a11a14a02e6 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4651,7 +4651,6 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
        .load_eoi_exitmap = svm_load_eoi_exitmap,
        .hwapic_irr_update = svm_hwapic_irr_update,
        .hwapic_isr_update = svm_hwapic_isr_update,
-       .sync_pir_to_irr = kvm_lapic_find_highest_irr,
        .apicv_post_state_restore = avic_post_state_restore,
 
        .set_tss_addr = svm_set_tss_addr,

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 817898eab7c3387809299a30d3cad4e0db813148..0ee1a039b490996959e137d5b5c53b22712bc36a 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4472,8 +4472,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu,
                                    struct kvm_lapic_state *s)
 {
-       if (vcpu->arch.apicv_active)
-               static_call(kvm_x86_sync_pir_to_irr)(vcpu);
+       static_call_cond(kvm_x86_sync_pir_to_irr)(vcpu);
 
        return kvm_apic_get_state(vcpu, s);
 }
@@ -9571,8 +9570,7 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
        if (irqchip_split(vcpu->kvm))
                kvm_scan_ioapic_routes(vcpu, vcpu->arch.ioapic_handled_vectors);
        else {
-               if (vcpu->arch.apicv_active)
-                       static_call(kvm_x86_sync_pir_to_irr)(vcpu);
+               static_call_cond(kvm_x86_sync_pir_to_irr)(vcpu);
                if (ioapic_in_kernel(vcpu->kvm))
                        kvm_ioapic_scan_entry(vcpu, vcpu->arch.ioapic_handled_vectors);
        }
@@ -9842,10 +9840,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
        /*
         * This handles the case where a posted interrupt was
-        * notified with kvm_vcpu_kick.
+        * notified with kvm_vcpu_kick.  Assigned devices can
+        * use the POSTED_INTR_VECTOR even if APICv is disabled,
+        * so do it even if APICv is disabled on this vCPU.
         */
-       if (kvm_lapic_enabled(vcpu) && vcpu->arch.apicv_active)
-               static_call(kvm_x86_sync_pir_to_irr)(vcpu);
+       if (kvm_lapic_enabled(vcpu))
+               static_call_cond(kvm_x86_sync_pir_to_irr)(vcpu);
 
        if (kvm_vcpu_exit_request(vcpu)) {
                vcpu->mode = OUTSIDE_GUEST_MODE;
@@ -9889,8 +9889,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
                if (likely(exit_fastpath != EXIT_FASTPATH_REENTER_GUEST))
                        break;
 
-               if (kvm_lapic_enabled(vcpu) && vcpu->arch.apicv_active)
-                       static_call(kvm_x86_sync_pir_to_irr)(vcpu);
+               if (kvm_lapic_enabled(vcpu))
+                       static_call_cond(kvm_x86_sync_pir_to_irr)(vcpu);
 
                if (unlikely(kvm_vcpu_exit_request(vcpu))) {
                        exit_fastpath = EXIT_FASTPATH_EXIT_HANDLED;