3 files changed, 73 insertions, 0 deletions

diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
index 2cc0120ccdb5..f9724dc8d079 100644
--- a/Documentation/kvm/api.txt
+++ b/Documentation/kvm/api.txt
@@ -813,6 +813,41 @@ This ioctl is required on Intel-based hosts.  This is needed on Intel hardware
 because of a quirk in the virtualization implementation (see the internals
 documentation when it pops into existence).
 
+4.36 KVM_ENABLE_CAP
+
+Capability: KVM_CAP_ENABLE_CAP
+Architectures: ppc
+Type: vcpu ioctl
+Parameters: struct kvm_enable_cap (in)
+Returns: 0 on success; -1 on error
+
++Not all extensions are enabled by default. Using this ioctl the application
+can enable an extension, making it available to the guest.
+
+On systems that do not support this ioctl, it always fails. On systems that
+do support it, it only works for extensions that are supported for enablement.
+
+To check if a capability can be enabled, the KVM_CHECK_EXTENSION ioctl should
+be used.
+
+struct kvm_enable_cap {
+       /* in */
+       __u32 cap;
+
+The capability that is supposed to get enabled.
+
+       __u32 flags;
+
+A bitfield indicating future enhancements. Has to be 0 for now.
+
+       __u64 args[4];
+
+Arguments for enabling a feature. If a feature needs initial values to
+function properly, this is the place to put them.
+
+       __u8  pad[64];
+};
+
 5. The kvm_run structure
 
 Application code obtains a pointer to the kvm_run structure by
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 0bb6a7e826d1..646bfd256e5d 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -150,6 +150,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_PPC_SEGSTATE:
         case KVM_CAP_PPC_PAIRED_SINGLES:
         case KVM_CAP_PPC_UNSET_IRQ:
+        case KVM_CAP_ENABLE_CAP:
                 r = 1;
                 break;
         case KVM_CAP_COALESCED_MMIO:
@@ -465,6 +466,23 @@ int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu, struct kvm_interrupt *irq)
         return 0;
 }
 
+static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
+                                     struct kvm_enable_cap *cap)
+{
+        int r;
+
+        if (cap->flags)
+                return -EINVAL;
+
+        switch (cap->cap) {
+        default:
+                r = -EINVAL;
+                break;
+        }
+
+        return r;
+}
+
 int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
                                     struct kvm_mp_state *mp_state)
 {
@@ -493,6 +511,15 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
                 r = kvm_vcpu_ioctl_interrupt(vcpu, &irq);
                 break;
         }
+        case KVM_ENABLE_CAP:
+        {
+                struct kvm_enable_cap cap;
+                r = -EFAULT;
+                if (copy_from_user(&cap, argp, sizeof(cap)))
+                        goto out;
+                r = kvm_vcpu_ioctl_enable_cap(vcpu, &cap);
+                break;
+        }
         default:
                 r = -EINVAL;
         }
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index c36d093e9806..ecb68e433558 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -400,6 +400,15 @@ struct kvm_ioeventfd {
         __u8  pad[36];
 };
 
+/* for KVM_ENABLE_CAP */
+struct kvm_enable_cap {
+        /* in */
+        __u32 cap;
+        __u32 flags;
+        __u64 args[4];
+        __u8  pad[64];
+};
+
 #define KVMIO 0xAE
 
 /*
@@ -508,6 +517,7 @@ struct kvm_ioeventfd {
 #endif
 #define KVM_CAP_X86_ROBUST_SINGLESTEP 51
 #define KVM_CAP_PPC_UNSET_IRQ 53
+#define KVM_CAP_ENABLE_CAP 54
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -697,6 +707,7 @@ struct kvm_clock_data {
 /* Available with KVM_CAP_DEBUGREGS */
 #define KVM_GET_DEBUGREGS         _IOR(KVMIO,  0xa1, struct kvm_debugregs)
 #define KVM_SET_DEBUGREGS         _IOW(KVMIO,  0xa2, struct kvm_debugregs)
+#define KVM_ENABLE_CAP            _IOW(KVMIO,  0xa3, struct kvm_enable_cap)
 
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU     (1 << 0)