MIPS: KVM: Implement PRid CP0 register access

Implement access to the guest Processor Identification CP0 register
using the KVM_GET_ONE_REG and KVM_SET_ONE_REG ioctls. This allows the
owning process to modify and read back the value that is exposed to the
guest in this register.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org

Documentation/virtual/kvm/api.txt

@@ -1967,6 +1967,7 @@ registers, find a list below:
   MIPS  | KVM_REG_MIPS_CP0_STATUS       | 32
   MIPS  | KVM_REG_MIPS_CP0_CAUSE        | 32
   MIPS  | KVM_REG_MIPS_CP0_EPC          | 64
+  MIPS  | KVM_REG_MIPS_CP0_PRID         | 32
   MIPS  | KVM_REG_MIPS_CP0_CONFIG       | 32
   MIPS  | KVM_REG_MIPS_CP0_CONFIG1      | 32
   MIPS  | KVM_REG_MIPS_CP0_CONFIG2      | 32

arch/mips/include/asm/kvm_host.h

@@ -42,6 +42,7 @@
 #define KVM_REG_MIPS_CP0_STATUS		MIPS_CP0_32(12, 0)
 #define KVM_REG_MIPS_CP0_CAUSE		MIPS_CP0_32(13, 0)
 #define KVM_REG_MIPS_CP0_EPC		MIPS_CP0_64(14, 0)
+#define KVM_REG_MIPS_CP0_PRID		MIPS_CP0_32(15, 0)
 #define KVM_REG_MIPS_CP0_EBASE		MIPS_CP0_64(15, 1)
 #define KVM_REG_MIPS_CP0_CONFIG		MIPS_CP0_32(16, 0)
 #define KVM_REG_MIPS_CP0_CONFIG1	MIPS_CP0_32(16, 1)

arch/mips/kvm/mips.c

@@ -505,6 +505,7 @@ static u64 kvm_mips_get_one_regs[] = {
 	KVM_REG_MIPS_CP0_STATUS,
 	KVM_REG_MIPS_CP0_CAUSE,
 	KVM_REG_MIPS_CP0_EPC,
+	KVM_REG_MIPS_CP0_PRID,
 	KVM_REG_MIPS_CP0_CONFIG,
 	KVM_REG_MIPS_CP0_CONFIG1,
 	KVM_REG_MIPS_CP0_CONFIG2,
@@ -574,6 +575,9 @@ static int kvm_mips_get_reg(struct kvm_vcpu *vcpu,
 	case KVM_REG_MIPS_CP0_EPC:
 		v = (long)kvm_read_c0_guest_epc(cop0);
 		break;
+	case KVM_REG_MIPS_CP0_PRID:
+		v = (long)kvm_read_c0_guest_prid(cop0);
+		break;
 	case KVM_REG_MIPS_CP0_ERROREPC:
 		v = (long)kvm_read_c0_guest_errorepc(cop0);
 		break;
@@ -687,6 +691,9 @@ static int kvm_mips_set_reg(struct kvm_vcpu *vcpu,
 	case KVM_REG_MIPS_CP0_EPC:
 		kvm_write_c0_guest_epc(cop0, v);
 		break;
+	case KVM_REG_MIPS_CP0_PRID:
+		kvm_write_c0_guest_prid(cop0, v);
+		break;
 	case KVM_REG_MIPS_CP0_ERROREPC:
 		kvm_write_c0_guest_errorepc(cop0, v);
 		break;