arm64: KVM: Support X-Gene guest VCPU on APM X-Gene host

This patch allows us to have X-Gene guest VCPU when using KVM arm64
on APM X-Gene host.

We add KVM_ARM_TARGET_XGENE_POTENZA for X-Gene Potenza compatible
guest VCPU and we return KVM_ARM_TARGET_XGENE_POTENZA in kvm_target_cpu()
when running on X-Gene host with Potenza core.

[maz: sanitized the commit log]
Signed-off-by: Anup Patel <anup.patel@linaro.org>
Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/include/uapi/asm/kvm.h

@@ -55,8 +55,9 @@ struct kvm_regs {
 #define KVM_ARM_TARGET_AEM_V8		0
 #define KVM_ARM_TARGET_FOUNDATION_V8	1
 #define KVM_ARM_TARGET_CORTEX_A57	2
+#define KVM_ARM_TARGET_XGENE_POTENZA	3
 
-#define KVM_ARM_NUM_TARGETS		3
+#define KVM_ARM_NUM_TARGETS		4
 
 /* KVM_ARM_SET_DEVICE_ADDR ioctl id encoding */
 #define KVM_ARM_DEVICE_TYPE_SHIFT	0

arch/arm64/kvm/guest.c

@@ -207,20 +207,26 @@ int __attribute_const__ kvm_target_cpu(void)
 	unsigned long implementor = read_cpuid_implementor();
 	unsigned long part_number = read_cpuid_part_number();
 
-	if (implementor != ARM_CPU_IMP_ARM)
-		return -EINVAL;
-
+	switch (implementor) {
+	case ARM_CPU_IMP_ARM:
 		switch (part_number) {
 		case ARM_CPU_PART_AEM_V8:
 			return KVM_ARM_TARGET_AEM_V8;
 		case ARM_CPU_PART_FOUNDATION:
 			return KVM_ARM_TARGET_FOUNDATION_V8;
 		case ARM_CPU_PART_CORTEX_A57:
-		/* Currently handled by the generic backend */
 			return KVM_ARM_TARGET_CORTEX_A57;
-	default:
+		};
+		break;
+	case ARM_CPU_IMP_APM:
+		switch (part_number) {
+		case APM_CPU_PART_POTENZA:
+			return KVM_ARM_TARGET_XGENE_POTENZA;
+		};
+		break;
+	};
+
 	return -EINVAL;
-	}
 }
 
 int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,

arch/arm64/kvm/sys_regs_generic_v8.c

@@ -90,6 +90,9 @@ static int __init sys_reg_genericv8_init(void)
 					  &genericv8_target_table);
 	kvm_register_target_sys_reg_table(KVM_ARM_TARGET_CORTEX_A57,
 					  &genericv8_target_table);
+	kvm_register_target_sys_reg_table(KVM_ARM_TARGET_XGENE_POTENZA,
+					  &genericv8_target_table);
+
 	return 0;
 }
 late_initcall(sys_reg_genericv8_init);