1 files changed, 68 insertions, 8 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 8b6ec3304100..a9845a1a9cd5 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -105,6 +105,63 @@ bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector)
 		apic_test_vector(vector, apic->regs + APIC_IRR);
 }
 
+static bool kvm_lapic_advertise_suppress_eoi_broadcast(struct kvm *kvm)
+{
+	switch (kvm->arch.suppress_eoi_broadcast_mode) {
+	case KVM_SUPPRESS_EOI_BROADCAST_ENABLED:
+		return true;
+	case KVM_SUPPRESS_EOI_BROADCAST_DISABLED:
+		return false;
+	case KVM_SUPPRESS_EOI_BROADCAST_QUIRKED:
+		/*
+		 * The default in-kernel I/O APIC emulates the 82093AA and does not
+		 * implement an EOI register. Some guests (e.g. Windows with the
+		 * Hyper-V role enabled) disable LAPIC EOI broadcast without
+		 * checking the I/O APIC version, which can cause level-triggered
+		 * interrupts to never be EOI'd.
+		 *
+		 * To avoid this, KVM doesn't advertise Suppress EOI Broadcast
+		 * support when using the default in-kernel I/O APIC.
+		 *
+		 * Historically, in split IRQCHIP mode, KVM always advertised
+		 * Suppress EOI Broadcast support but did not actually suppress
+		 * EOIs, resulting in quirky behavior.
+		 */
+		return !ioapic_in_kernel(kvm);
+	default:
+		WARN_ON_ONCE(1);
+		return false;
+	}
+}
+
+bool kvm_lapic_suppress_eoi_broadcast(struct kvm_lapic *apic)
+{
+	struct kvm *kvm = apic->vcpu->kvm;
+
+	if (!(kvm_lapic_get_reg(apic, APIC_SPIV) & APIC_SPIV_DIRECTED_EOI))
+		return false;
+
+	switch (kvm->arch.suppress_eoi_broadcast_mode) {
+	case KVM_SUPPRESS_EOI_BROADCAST_ENABLED:
+		return true;
+	case KVM_SUPPRESS_EOI_BROADCAST_DISABLED:
+		return false;
+	case KVM_SUPPRESS_EOI_BROADCAST_QUIRKED:
+		/*
+		 * Historically, in split IRQCHIP mode, KVM ignored the suppress
+		 * EOI broadcast bit set by the guest and broadcasts EOIs to the
+		 * userspace I/O APIC. For In-kernel I/O APIC, the support itself
+		 * is not advertised, can only be enabled via KVM_SET_APIC_STATE,
+		 * and KVM's I/O APIC doesn't emulate Directed EOIs; but if the
+		 * feature is enabled, it is respected (with odd behavior).
+		 */
+		return ioapic_in_kernel(kvm);
+	default:
+		WARN_ON_ONCE(1);
+		return false;
+	}
+}
+
 __read_mostly DEFINE_STATIC_KEY_FALSE(kvm_has_noapic_vcpu);
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_has_noapic_vcpu);
 
@@ -554,15 +611,9 @@ void kvm_apic_set_version(struct kvm_vcpu *vcpu)
 
 	v = APIC_VERSION | ((apic->nr_lvt_entries - 1) << 16);
 
-	/*
-	 * KVM emulates 82093AA datasheet (with in-kernel IOAPIC implementation)
-	 * which doesn't have EOI register; Some buggy OSes (e.g. Windows with
-	 * Hyper-V role) disable EOI broadcast in lapic not checking for IOAPIC
-	 * version first and level-triggered interrupts never get EOIed in
-	 * IOAPIC.
-	 */
+
 	if (guest_cpu_cap_has(vcpu, X86_FEATURE_X2APIC) &&
-	    !ioapic_in_kernel(vcpu->kvm))
+	    kvm_lapic_advertise_suppress_eoi_broadcast(vcpu->kvm))
 		v |= APIC_LVR_DIRECTED_EOI;
 	kvm_lapic_set_reg(apic, APIC_LVR, v);
 }
@@ -1517,6 +1568,15 @@ static void kvm_ioapic_send_eoi(struct kvm_lapic *apic, int vector)
 
 	/* Request a KVM exit to inform the userspace IOAPIC. */
 	if (irqchip_split(apic->vcpu->kvm)) {
+		/*
+		 * Don't exit to userspace if the guest has enabled Directed
+		 * EOI, a.k.a. Suppress EOI Broadcasts, in which case the local
+		 * APIC doesn't broadcast EOIs (the guest must EOI the target
+		 * I/O APIC(s) directly).
+		 */
+		if (kvm_lapic_suppress_eoi_broadcast(apic))
+			return;
+
 		apic->vcpu->arch.pending_ioapic_eoi = vector;
 		kvm_make_request(KVM_REQ_IOAPIC_EOI_EXIT, apic->vcpu);
 		return;