KVM: arm64: gic-v5: Support GICv5 interrupts with KVM_IRQ_LINE

Interrupts under GICv5 look quite different to those from older Arm
GICs. Specifically, the type is encoded in the top bits of the
interrupt ID.

Extend KVM_IRQ_LINE to cope with GICv5 PPIs and SPIs. The requires
subtly changing the KVM_IRQ_LINE API for GICv5 guests. For older Arm
GICs, PPIs had to be in the range of 16-31, and SPIs had to be
32-1019, but this no longer holds true for GICv5. Instead, for a GICv5
guest support PPIs in the range of 0-127, and SPIs in the range
0-65535. The documentation is updated accordingly.

The SPI range doesn't cover the full SPI range that a GICv5 system can
potentially cope with (GICv5 provides up to 24-bits of SPI ID space,
and we only have 16 bits to work with in KVM_IRQ_LINE). However, 65k
SPIs is more than would be reasonably expected on systems for years to
come.

In order to use vgic_is_v5(), the kvm/arm_vgic.h header is added to
kvm/arm.c.

Note: As the GICv5 KVM implementation currently doesn't support
injecting SPIs attempts to do so will fail. This restriction will by
lifted as the GICv5 KVM support evolves.

Co-authored-by: Timothy Hayes <timothy.hayes@arm.com>
Signed-off-by: Timothy Hayes <timothy.hayes@arm.com>
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20260319154937.3619520-28-sascha.bischoff@arm.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

Documentation/virt/kvm/api.rst

@@ -907,10 +907,12 @@ The irq_type field has the following values:
 - KVM_ARM_IRQ_TYPE_CPU:
 	       out-of-kernel GIC: irq_id 0 is IRQ, irq_id 1 is FIQ
 - KVM_ARM_IRQ_TYPE_SPI:
-	       in-kernel GIC: SPI, irq_id between 32 and 1019 (incl.)
+	       in-kernel GICv2/GICv3: SPI, irq_id between 32 and 1019 (incl.)
                (the vcpu_index field is ignored)
+	       in-kernel GICv5: SPI, irq_id between 0 and 65535 (incl.)
 - KVM_ARM_IRQ_TYPE_PPI:
-	       in-kernel GIC: PPI, irq_id between 16 and 31 (incl.)
+	       in-kernel GICv2/GICv3: PPI, irq_id between 16 and 31 (incl.)
+	       in-kernel GICv5: PPI, irq_id between 0 and 127 (incl.)
 
 (The irq_id field thus corresponds nicely to the IRQ ID in the ARM GIC specs)
 

arch/arm64/kvm/arm.c

@@ -45,6 +45,9 @@
 #include <kvm/arm_hypercalls.h>
 #include <kvm/arm_pmu.h>
 #include <kvm/arm_psci.h>
+#include <kvm/arm_vgic.h>
+
+#include <linux/irqchip/arm-gic-v5.h>
 
 #include "sys_regs.h"
 
@@ -1479,16 +1482,29 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level,
 		if (!vcpu)
 			return -EINVAL;
 
-		if (irq_num < VGIC_NR_SGIS || irq_num >= VGIC_NR_PRIVATE_IRQS)
+		if (vgic_is_v5(kvm)) {
+			if (irq_num >= VGIC_V5_NR_PRIVATE_IRQS)
+				return -EINVAL;
+
+			/* Build a GICv5-style IntID here */
+			irq_num = vgic_v5_make_ppi(irq_num);
+		} else if (irq_num < VGIC_NR_SGIS ||
+			   irq_num >= VGIC_NR_PRIVATE_IRQS) {
 			return -EINVAL;
+		}
 
 		return kvm_vgic_inject_irq(kvm, vcpu, irq_num, level, NULL);
 	case KVM_ARM_IRQ_TYPE_SPI:
 		if (!irqchip_in_kernel(kvm))
 			return -ENXIO;
 
-		if (irq_num < VGIC_NR_PRIVATE_IRQS)
-			return -EINVAL;
+		if (vgic_is_v5(kvm)) {
+			/* Build a GICv5-style IntID here */
+			irq_num = vgic_v5_make_spi(irq_num);
+		} else {
+			if (irq_num < VGIC_NR_PRIVATE_IRQS)
+				return -EINVAL;
+		}
 
 		return kvm_vgic_inject_irq(kvm, NULL, irq_num, level, NULL);
 	}

arch/arm64/kvm/vgic/vgic.c

@@ -86,6 +86,10 @@ static struct vgic_irq *vgic_get_lpi(struct kvm *kvm, u32 intid)
  */
 struct vgic_irq *vgic_get_irq(struct kvm *kvm, u32 intid)
 {
+	/* Non-private IRQs are not yet implemented for GICv5 */
+	if (vgic_is_v5(kvm))
+		return NULL;
+
 	/* SPIs */
 	if (intid >= VGIC_NR_PRIVATE_IRQS &&
 	    intid < (kvm->arch.vgic.nr_spis + VGIC_NR_PRIVATE_IRQS)) {