[PATCH RFC 09/39] KVM: x86: declare Xen HVM guest capability

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

Also take the chance to document this rather old capability of
KVM_CAP_XEN_HVM which only means it supports the Xen hypercall MSR.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 Documentation/virtual/kvm/api.txt | 14 ++++++++++++++
 arch/x86/kvm/x86.c                |  1 +
 include/uapi/linux/kvm.h          |  3 +++
 3 files changed, 18 insertions(+)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 356156f5c52d..c3a1402b76bf 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -5016,6 +5016,7 @@ CPU when the exception is taken. If this virtual SError is taken to EL1 using
 AArch64, this value will be reported in the ISS field of ESR_ELx.
 
 See KVM_CAP_VCPU_EVENTS for more details.
+
 8.20 KVM_CAP_HYPERV_SEND_IPI
 
 Architectures: x86
@@ -5023,3 +5024,16 @@ Architectures: x86
 This capability indicates that KVM supports paravirtualized Hyper-V IPI send
 hypercalls:
 HvCallSendSyntheticClusterIpi, HvCallSendSyntheticClusterIpiEx.
+
+8.21 KVM_CAP_XEN_HVM
+
+Architectures: x86
+
+This capability indicates that KVM supports the Xen hypercall page MSR.
+
+8.22 KVM_CAP_XEN_HVM_GUEST
+
+Architectures: x86
+
+This capability indicates that KVM supports Xen HVM guests.
+This includes KVM_IRQ_ROUTING_XEN_EVTCHN as well.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 888598fdf543..11b9ff2bd901 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3009,6 +3009,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_PIT_STATE2:
 	case KVM_CAP_SET_IDENTITY_MAP_ADDR:
 	case KVM_CAP_XEN_HVM:
+	case KVM_CAP_XEN_HVM_GUEST:
 	case KVM_CAP_VCPU_EVENTS:
 	case KVM_CAP_HYPERV:
 	case KVM_CAP_HYPERV_VAPIC:
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index b91e57d9e6d3..682ea00abd58 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1003,6 +1003,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_ARM_VM_IPA_SIZE 165
 #define KVM_CAP_MANUAL_DIRTY_LOG_PROTECT 166
 #define KVM_CAP_HYPERV_CPUID 167
+#define KVM_CAP_XEN_HVM_GUEST 168
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -1455,6 +1456,7 @@ struct kvm_enc_region {
 /* Available with KVM_CAP_HYPERV_CPUID */
 #define KVM_GET_SUPPORTED_HV_CPUID _IOWR(KVMIO, 0xc1, struct kvm_cpuid2)
 
+/* Available with KVM_CAP_XEN_HVM_GUEST */
 #define KVM_XEN_HVM_GET_ATTR        _IOWR(KVMIO,  0xc2, struct kvm_xen_hvm_attr)
 #define KVM_XEN_HVM_SET_ATTR        _IOW(KVMIO,  0xc3, struct kvm_xen_hvm_attr)
 
@@ -1472,6 +1474,7 @@ struct kvm_xen_hvm_attr {
 	} u;
 };
 
+/* Available with KVM_CAP_XEN_HVM_GUEST */
 #define KVM_XEN_ATTR_TYPE_SHARED_INFO       0x0
 #define KVM_XEN_ATTR_TYPE_VCPU_INFO         0x1
 #define KVM_XEN_ATTR_TYPE_VCPU_TIME_INFO    0x2
-- 
2.11.0