KVM: arm/arm64: vgic-new: Add PRIORITY registers handlers

The priority register handlers are shared between the v2 and v3
emulation, so their implementation goes into vgic-mmio.c, to be
easily referenced from the v3 emulation as well later.
There is a corner case when we change the priority of a pending
interrupt which we don't handle at the moment.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>

virt/kvm/arm/vgic/vgic-mmio-v2.c

@@ -90,7 +90,7 @@ static const struct vgic_register_region vgic_v2_dist_registers[] = {
 		vgic_mmio_read_active, vgic_mmio_write_cactive, 1,
 		VGIC_ACCESS_32bit),
 	REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_PRI,
-		vgic_mmio_read_raz, vgic_mmio_write_wi, 8,
+		vgic_mmio_read_priority, vgic_mmio_write_priority, 8,
 		VGIC_ACCESS_32bit | VGIC_ACCESS_8bit),
 	REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_TARGET,
 		vgic_mmio_read_raz, vgic_mmio_write_wi, 8,

virt/kvm/arm/vgic/vgic-mmio.c

@@ -236,6 +236,46 @@ void vgic_mmio_write_sactive(struct kvm_vcpu *vcpu,
 	}
 }
 
+unsigned long vgic_mmio_read_priority(struct kvm_vcpu *vcpu,
+				      gpa_t addr, unsigned int len)
+{
+	u32 intid = VGIC_ADDR_TO_INTID(addr, 8);
+	int i;
+	u64 val = 0;
+
+	for (i = 0; i < len; i++) {
+		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
+
+		val |= (u64)irq->priority << (i * 8);
+	}
+
+	return val;
+}
+
+/*
+ * We currently don't handle changing the priority of an interrupt that
+ * is already pending on a VCPU. If there is a need for this, we would
+ * need to make this VCPU exit and re-evaluate the priorities, potentially
+ * leading to this interrupt getting presented now to the guest (if it has
+ * been masked by the priority mask before).
+ */
+void vgic_mmio_write_priority(struct kvm_vcpu *vcpu,
+			      gpa_t addr, unsigned int len,
+			      unsigned long val)
+{
+	u32 intid = VGIC_ADDR_TO_INTID(addr, 8);
+	int i;
+
+	for (i = 0; i < len; i++) {
+		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
+
+		spin_lock(&irq->irq_lock);
+		/* Narrow the priority range to what we actually support */
+		irq->priority = (val >> (i * 8)) & GENMASK(7, 8 - VGIC_PRI_BITS);
+		spin_unlock(&irq->irq_lock);
+	}
+}
+
 static int match_region(const void *key, const void *elt)
 {
 	const unsigned int offset = (unsigned long)key;

virt/kvm/arm/vgic/vgic-mmio.h

@@ -129,6 +129,13 @@ void vgic_mmio_write_sactive(struct kvm_vcpu *vcpu,
 			     gpa_t addr, unsigned int len,
 			     unsigned long val);
 
+unsigned long vgic_mmio_read_priority(struct kvm_vcpu *vcpu,
+				      gpa_t addr, unsigned int len);
+
+void vgic_mmio_write_priority(struct kvm_vcpu *vcpu,
+			      gpa_t addr, unsigned int len,
+			      unsigned long val);
+
 unsigned int vgic_v2_init_dist_iodev(struct vgic_io_device *dev);
 
 #endif

virt/kvm/arm/vgic/vgic.h

@@ -19,6 +19,8 @@
 #define PRODUCT_ID_KVM		0x4b	/* ASCII code K */
 #define IMPLEMENTER_ARM		0x43b
 
+#define VGIC_PRI_BITS		5
+
 #define vgic_irq_is_sgi(intid) ((intid) < VGIC_NR_SGIS)
 
 struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,