[PATCH RFC 39/39] KVM: x86: declare Xen HVM Dom0 capability

[Joao Martins <joao.m.martins@oracle.com>]

Add new capability for domid, interdomain/unbound event channel types
and grant table support in hypervisor. This would be used to drive Xen
kernel backends.

Co-developed-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
 Documentation/virtual/kvm/api.txt | 10 ++++++++++
 arch/x86/kvm/x86.c                |  4 ++++
 include/uapi/linux/kvm.h          |  3 +++
 3 files changed, 17 insertions(+)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 36d9386415fa..311dcded5e28 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -5046,3 +5046,13 @@ This capability indicates KVM's support for the event channel offload.
 Implies support for KVM_IRQ_ROUTING_XEN_EVTCHN irq routing, and
 for attribute KVM_XEN_ATTR_TYPE_EVTCHN in KVM_XEN_HVM_GET_ATTR or
 KVM_XEN_HVM_SET_ATTR.
+
+8.24 KVM_CAP_XEN_HVM_DOM0
+
+Architectures: x86
+
+This capability indicates support for assigning domid and handling kernel
+backends in the hypervisor. Also implies that attributes
+KVM_XEN_ATTR_TYPE_DOMID, KVM_XEN_ATTR_TYPE_GNTTAB are supported.  For the
+existing KVM_XEN_ATTR_TYPE_EVTCHN attribute, it indicates support for
+interdomain and unbound event channels.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cb95f7f8bed9..e8c3494b10cb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -71,6 +71,7 @@
 #include <asm/mshyperv.h>
 #include <asm/hypervisor.h>
 #include <asm/intel_pt.h>
+#include <xen/xen.h>
 
 #define CREATE_TRACE_POINTS
 #include "trace.h"
@@ -3049,6 +3050,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_ADJUST_CLOCK:
 		r = KVM_CLOCK_TSC_STABLE;
 		break;
+	case KVM_CAP_XEN_HVM_DOM0:
+		r = xen_shim_domain();
+		break;
 	case KVM_CAP_X86_DISABLE_EXITS:
 		r |=  KVM_X86_DISABLE_EXITS_HLT | KVM_X86_DISABLE_EXITS_PAUSE;
 		if(kvm_can_mwait_in_guest())
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 74d877792dfa..d817a7bbf507 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1005,6 +1005,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_HYPERV_CPUID 167
 #define KVM_CAP_XEN_HVM_GUEST 168
 #define KVM_CAP_XEN_HVM_EVTCHN 169
+#define KVM_CAP_XEN_HVM_DOM0 170
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -1485,6 +1486,7 @@ struct kvm_xen_hvm_attr {
 
 #define XEN_EVTCHN_TYPE_VIRQ      0
 #define XEN_EVTCHN_TYPE_IPI       1
+/* Available with KVM_CAP_XEN_HVM_DOM0 */
 #define XEN_EVTCHN_TYPE_INTERDOM  2
 #define XEN_EVTCHN_TYPE_UNBOUND   3
 			__u32 type;
@@ -1536,6 +1538,7 @@ struct kvm_xen_hvm_attr {
 #define KVM_XEN_ATTR_TYPE_VCPU_RUNSTATE     0x3
 /* Available with KVM_CAP_XEN_HVM_EVTCHN */
 #define KVM_XEN_ATTR_TYPE_EVTCHN            0x4
+/* Available with KVM_CAP_XEN_HVM_DOM0 */
 #define KVM_XEN_ATTR_TYPE_DOMID             0x5
 #define KVM_XEN_ATTR_TYPE_GNTTAB            0x6
 
-- 
2.11.0