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

BugLink: https://bugs.launchpad.net/bugs/1956791
commit 37c4dbf337c5c2cdb24365ffae6ed70ac1e74d7a upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 17fa4ab1b834423a37147622f598dc5020da2361..8cc30fd0fdbfd201efb769164ec4b3321ef62e6f 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -704,7 +704,7 @@ 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 fa49b433c42c9ef36fd9c5710f33d9b5738166a1..17594391c06f995bc085b7c41a3b344a471d2488 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4530,7 +4530,6 @@ 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 ee0e827a044530560dc1e992b22b4dc81a9b9506..ba182596cc0192e84517ac4f8dbf1399091fccb8 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4300,8 +4300,7 @@ 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);
 }
@@ -9176,8 +9175,7 @@ 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);
        }
@@ -9435,10 +9433,12 @@ 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;
@@ -9476,8 +9476,8 @@ 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;