KVM: PPC: Book3S HV: Add one-reg interface to virtual PTCR register

This adds a one-reg register identifier which can be used to read and
set the virtual PTCR for the guest.  This register identifies the
address and size of the virtual partition table for the guest, which
contains information about the nested guests under this guest.

Migrating this value is the only extra requirement for migrating a
guest which has nested guests (assuming of course that the destination
host supports nested virtualization in the kvm-hv module).

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Documentation/virtual/kvm/api.txt

@@ -1922,6 +1922,7 @@ registers, find a list below:
   PPC   | KVM_REG_PPC_TIDR              | 64
   PPC   | KVM_REG_PPC_PSSCR             | 64
   PPC   | KVM_REG_PPC_DEC_EXPIRY        | 64
+  PPC   | KVM_REG_PPC_PTCR              | 64
   PPC   | KVM_REG_PPC_TM_GPR0           | 64
           ...
   PPC   | KVM_REG_PPC_TM_GPR31          | 64

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

@@ -634,6 +634,7 @@ struct kvm_ppc_cpu_char {
 
 #define KVM_REG_PPC_DEC_EXPIRY	(KVM_REG_PPC | KVM_REG_SIZE_U64 | 0xbe)
 #define KVM_REG_PPC_ONLINE	(KVM_REG_PPC | KVM_REG_SIZE_U32 | 0xbf)
+#define KVM_REG_PPC_PTCR	(KVM_REG_PPC | KVM_REG_SIZE_U64 | 0xc0)
 
 /* Transactional Memory checkpointed state:
  * This is all GPRs, all VSX regs and a subset of SPRs

arch/powerpc/kvm/book3s_hv.c

@@ -1710,6 +1710,9 @@ static int kvmppc_get_one_reg_hv(struct kvm_vcpu *vcpu, u64 id,
 	case KVM_REG_PPC_ONLINE:
 		*val = get_reg_val(id, vcpu->arch.online);
 		break;
+	case KVM_REG_PPC_PTCR:
+		*val = get_reg_val(id, vcpu->kvm->arch.l1_ptcr);
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -1941,6 +1944,9 @@ static int kvmppc_set_one_reg_hv(struct kvm_vcpu *vcpu, u64 id,
 			atomic_dec(&vcpu->arch.vcore->online_count);
 		vcpu->arch.online = i;
 		break;
+	case KVM_REG_PPC_PTCR:
+		vcpu->kvm->arch.l1_ptcr = set_reg_val(id, *val);
+		break;
 	default:
 		r = -EINVAL;
 		break;