KVM: PPC: Add KVM_CAP_NR_VCPUS and KVM_CAP_MAX_VCPUS

PPC KVM lacks these two capabilities, and as such a userland system must assume
a max of 4 VCPUs (following api.txt).  With these, a userland can determine
a more realistic limit.

Signed-off-by: Matt Evans <matt@ozlabs.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/powerpc/kvm/powerpc.c

@@ -249,6 +249,22 @@ int kvm_dev_ioctl_check_extension(long ext)
 		r = cpu_has_feature(CPU_FTR_ARCH_206) ? 1 : 0;
 		break;
 #endif
+	case KVM_CAP_NR_VCPUS:
+		/*
+		 * Recommending a number of CPUs is somewhat arbitrary; we
+		 * return the number of present CPUs for -HV (since a host
+		 * will have secondary threads "offline"), and for other KVM
+		 * implementations just count online CPUs.
+		 */
+#ifdef CONFIG_KVM_BOOK3S_64_HV
+		r = num_present_cpus();
+#else
+		r = num_online_cpus();
+#endif
+		break;
+	case KVM_CAP_MAX_VCPUS:
+		r = KVM_MAX_VCPUS;
+		break;
 	default:
 		r = 0;
 		break;