KVM: arm64: Disambiguate support for vSGIs v. vLPIs

vgic_supports_direct_msis() is a bit of a misnomer, as it returns true
if either vSGIs or vLPIs are supported. Pick it apart into a few
predicates and replace some open-coded checks for vSGIs, including an
opportunistic fix to always check if the CPUIF is capable of handling
vSGIs.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250724062805.2658919-2-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: oupton

arch/arm64/kvm/vgic/vgic-init.c

@@ -391,11 +391,10 @@ int vgic_init(struct kvm *kvm)
 		goto out;
 
 	/*
-	 * If we have GICv4.1 enabled, unconditionally request enable the
-	 * v4 support so that we get HW-accelerated vSGIs. Otherwise, only
-	 * enable it if we present a virtual ITS to the guest.
+	 * Ensure vPEs are allocated if direct IRQ injection (e.g. vSGIs,
+	 * vLPIs) is supported.
 	 */
-	if (vgic_supports_direct_msis(kvm)) {
+	if (vgic_supports_direct_irqs(kvm)) {
 		ret = vgic_v4_init(kvm);
 		if (ret)
 			goto out;
@@ -443,7 +442,7 @@ static void kvm_vgic_dist_destroy(struct kvm *kvm)
 		dist->vgic_cpu_base = VGIC_ADDR_UNDEF;
 	}
 
-	if (vgic_supports_direct_msis(kvm))
+	if (vgic_supports_direct_irqs(kvm))
 		vgic_v4_teardown(kvm);
 
 	xa_destroy(&dist->lpi_xa);

arch/arm64/kvm/vgic/vgic-mmio-v3.c

@@ -50,8 +50,12 @@ bool vgic_has_its(struct kvm *kvm)
 
 bool vgic_supports_direct_msis(struct kvm *kvm)
 {
-	return (kvm_vgic_global_state.has_gicv4_1 ||
-		(kvm_vgic_global_state.has_gicv4 && vgic_has_its(kvm)));
+	return kvm_vgic_global_state.has_gicv4 && vgic_has_its(kvm);
+}
+
+bool vgic_supports_direct_sgis(struct kvm *kvm)
+{
+	return kvm_vgic_global_state.has_gicv4_1 && gic_cpuif_has_vsgi();
 }
 
 /*
@@ -86,7 +90,7 @@ static unsigned long vgic_mmio_read_v3_misc(struct kvm_vcpu *vcpu,
 		}
 		break;
 	case GICD_TYPER2:
-		if (kvm_vgic_global_state.has_gicv4_1 && gic_cpuif_has_vsgi())
+		if (vgic_supports_direct_sgis(vcpu->kvm))
 			value = GICD_TYPER2_nASSGIcap;
 		break;
 	case GICD_IIDR:
@@ -119,7 +123,7 @@ static void vgic_mmio_write_v3_misc(struct kvm_vcpu *vcpu,
 		dist->enabled = val & GICD_CTLR_ENABLE_SS_G1;
 
 		/* Not a GICv4.1? No HW SGIs */
-		if (!kvm_vgic_global_state.has_gicv4_1 || !gic_cpuif_has_vsgi())
+		if (!vgic_supports_direct_sgis(vcpu->kvm))
 			val &= ~GICD_CTLR_nASSGIreq;
 
 		/* Dist stays enabled? nASSGIreq is RO */
@@ -133,7 +137,7 @@ static void vgic_mmio_write_v3_misc(struct kvm_vcpu *vcpu,
 		if (is_hwsgi != dist->nassgireq)
 			vgic_v4_configure_vsgis(vcpu->kvm);
 
-		if (kvm_vgic_global_state.has_gicv4_1 &&
+		if (vgic_supports_direct_sgis(vcpu->kvm) &&
 		    was_enabled != dist->enabled)
 			kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_RELOAD_GICv4);
 		else if (!was_enabled && dist->enabled)
@@ -178,7 +182,7 @@ static int vgic_mmio_uaccess_write_v3_misc(struct kvm_vcpu *vcpu,
 		}
 	case GICD_CTLR:
 		/* Not a GICv4.1? No HW SGIs */
-		if (!kvm_vgic_global_state.has_gicv4_1)
+		if (!vgic_supports_direct_sgis(vcpu->kvm))
 			val &= ~GICD_CTLR_nASSGIreq;
 
 		dist->enabled = val & GICD_CTLR_ENABLE_SS_G1;

arch/arm64/kvm/vgic/vgic-v4.c

@@ -356,7 +356,7 @@ int vgic_v4_put(struct kvm_vcpu *vcpu)
 {
 	struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
 
-	if (!vgic_supports_direct_msis(vcpu->kvm) || !vpe->resident)
+	if (!vgic_supports_direct_irqs(vcpu->kvm) || !vpe->resident)
 		return 0;
 
 	return its_make_vpe_non_resident(vpe, vgic_v4_want_doorbell(vcpu));
@@ -367,7 +367,7 @@ int vgic_v4_load(struct kvm_vcpu *vcpu)
 	struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
 	int err;
 
-	if (!vgic_supports_direct_msis(vcpu->kvm) || vpe->resident)
+	if (!vgic_supports_direct_irqs(vcpu->kvm) || vpe->resident)
 		return 0;
 
 	if (vcpu_get_flag(vcpu, IN_WFI))

arch/arm64/kvm/vgic/vgic.c

@@ -951,7 +951,7 @@ void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu)
 	 * can be directly injected (GICv4).
 	 */
 	if (list_empty(&vcpu->arch.vgic_cpu.ap_list_head) &&
-	    !vgic_supports_direct_msis(vcpu->kvm))
+	    !vgic_supports_direct_irqs(vcpu->kvm))
 		return;
 
 	DEBUG_SPINLOCK_BUG_ON(!irqs_disabled());
@@ -965,7 +965,7 @@ void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu)
 	if (can_access_vgic_from_kernel())
 		vgic_restore_state(vcpu);
 
-	if (vgic_supports_direct_msis(vcpu->kvm))
+	if (vgic_supports_direct_irqs(vcpu->kvm))
 		vgic_v4_commit(vcpu);
 }
 

arch/arm64/kvm/vgic/vgic.h

@@ -370,6 +370,13 @@ int vgic_its_inv_lpi(struct kvm *kvm, struct vgic_irq *irq);
 int vgic_its_invall(struct kvm_vcpu *vcpu);
 
 bool vgic_supports_direct_msis(struct kvm *kvm);
+bool vgic_supports_direct_sgis(struct kvm *kvm);
+
+static inline bool vgic_supports_direct_irqs(struct kvm *kvm)
+{
+	return vgic_supports_direct_msis(kvm) || vgic_supports_direct_sgis(kvm);
+}
+
 int vgic_v4_init(struct kvm *kvm);
 void vgic_v4_teardown(struct kvm *kvm);
 void vgic_v4_configure_vsgis(struct kvm *kvm);