KVM: PPC: Book3S: Add GET/SET_ONE_REG interface for VRSAVE

The VRSAVE register value for a vcpu is accessible through the
GET/SET_SREGS interface for Book E processors, but not for Book 3S
processors.  In order to make this accessible for Book 3S processors,
this adds a new register identifier for GET/SET_ONE_REG, and adds
the code to implement it.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

Documentation/virtual/kvm/api.txt

@@ -1834,6 +1834,7 @@ registers, find a list below:
   PPC   | KVM_REG_PPC_TCSCR	| 64
   PPC   | KVM_REG_PPC_PID	| 64
   PPC   | KVM_REG_PPC_ACOP	| 64
+  PPC   | KVM_REG_PPC_VRSAVE	| 32
   PPC   | KVM_REG_PPC_TM_GPR0	| 64
           ...
   PPC   | KVM_REG_PPC_TM_GPR31	| 64

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

@@ -532,6 +532,8 @@ struct kvm_get_htab_header {
 #define KVM_REG_PPC_PID		(KVM_REG_PPC | KVM_REG_SIZE_U64 | 0xb2)
 #define KVM_REG_PPC_ACOP	(KVM_REG_PPC | KVM_REG_SIZE_U64 | 0xb3)
 
+#define KVM_REG_PPC_VRSAVE	(KVM_REG_PPC | KVM_REG_SIZE_U32 | 0xb4)
+
 /* Transactional Memory checkpointed state:
  * This is all GPRs, all VSX regs and a subset of SPRs
  */

arch/powerpc/kvm/book3s.c

@@ -528,6 +528,9 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 			}
 			val = get_reg_val(reg->id, vcpu->arch.vscr.u[3]);
 			break;
+		case KVM_REG_PPC_VRSAVE:
+			val = get_reg_val(reg->id, vcpu->arch.vrsave);
+			break;
 #endif /* CONFIG_ALTIVEC */
 		case KVM_REG_PPC_DEBUG_INST: {
 			u32 opcode = INS_TW;
@@ -605,6 +608,13 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 			}
 			vcpu->arch.vscr.u[3] = set_reg_val(reg->id, val);
 			break;
+		case KVM_REG_PPC_VRSAVE:
+			if (!cpu_has_feature(CPU_FTR_ALTIVEC)) {
+				r = -ENXIO;
+				break;
+			}
+			vcpu->arch.vrsave = set_reg_val(reg->id, val);
+			break;
 #endif /* CONFIG_ALTIVEC */
 #ifdef CONFIG_KVM_XICS
 		case KVM_REG_PPC_ICP_STATE: