KVM: arm64: GICv3: mandate page-aligned GICV region

Just like GICv2 was fixed in 63afbe7a0ac1
(kvm: arm64: vgic: fix hyp panic with 64k pages on juno platform),
mandate the GICV region to be both aligned on a page boundary and
its size to be a multiple of page size.

This prevents a guest from being able to poke at regions where we
have no idea what is sitting there.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

virt/kvm/arm/vgic-v3.c

@@ -215,6 +215,22 @@ int vgic_v3_probe(struct device_node *vgic_node,
 		ret = -ENXIO;
 		goto out;
 	}
+
+	if (!PAGE_ALIGNED(vcpu_res.start)) {
+		kvm_err("GICV physical address 0x%llx not page aligned\n",
+			(unsigned long long)vcpu_res.start);
+		ret = -ENXIO;
+		goto out;
+	}
+
+	if (!PAGE_ALIGNED(resource_size(&vcpu_res))) {
+		kvm_err("GICV size 0x%llx not a multiple of page size 0x%lx\n",
+			(unsigned long long)resource_size(&vcpu_res),
+			PAGE_SIZE);
+		ret = -ENXIO;
+		goto out;
+	}
+
 	vgic->vcpu_base = vcpu_res.start;
 	vgic->vctrl_base = NULL;
 	vgic->type = VGIC_V3;