KVM: x86: Add KVM_CAP_X86_ROBUST_SINGLESTEP

This marks the guest single-step API improvement of 94fe45da and
91586a3b with a capability flag to allow reliable detection by user
space.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Cc: stable@kernel.org (2.6.33)
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c3d2acb..e46282a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1570,6 +1570,7 @@
 	case KVM_CAP_HYPERV_VAPIC:
 	case KVM_CAP_HYPERV_SPIN:
 	case KVM_CAP_PCI_SEGMENT:
+	case KVM_CAP_X86_ROBUST_SINGLESTEP:
 		r = 1;
 		break;
 	case KVM_CAP_COALESCED_MMIO: