[RFC PATCH v6 09/92] kvm: introspection: add KVMI_GET_GUEST_INFO

[Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>]

From: Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>

For now, this command returns only the number of online vCPUs.

Signed-off-by: Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
 Documentation/virtual/kvm/kvmi.rst | 18 ++++++++++++++++++
 include/uapi/linux/kvmi.h          |  5 +++++
 virt/kvm/kvmi_msg.c                | 14 ++++++++++++++
 3 files changed, 37 insertions(+)

diff --git a/Documentation/virtual/kvm/kvmi.rst b/Documentation/virtual/kvm/kvmi.rst
index 61cf69aa5d07..2fbe7c28e4f1 100644
--- a/Documentation/virtual/kvm/kvmi.rst
+++ b/Documentation/virtual/kvm/kvmi.rst
@@ -362,3 +362,21 @@ This command is always allowed.
 
 * -KVM_PERM - the event specified by ``id`` is disallowed
 * -KVM_EINVAL - padding is not zero
+
+5. KVMI_GET_GUEST_INFO
+----------------------
+
+:Architectures: all
+:Versions: >= 1
+:Parameters:: none
+:Returns:
+
+::
+
+	struct kvmi_error_code;
+	struct kvmi_get_guest_info_reply {
+		__u32 vcpu_count;
+		__u32 padding[3];
+	};
+
+Returns the number of online vCPUs.
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index 7390303371c9..367c8ec28f75 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -102,4 +102,9 @@ struct kvmi_check_event {
 	__u32 padding2;
 };
 
+struct kvmi_get_guest_info_reply {
+	__u32 vcpu_count;
+	__u32 padding[3];
+};
+
 #endif /* _UAPI__LINUX_KVMI_H */
diff --git a/virt/kvm/kvmi_msg.c b/virt/kvm/kvmi_msg.c
index e24996611e3a..cf8a120b0eae 100644
--- a/virt/kvm/kvmi_msg.c
+++ b/virt/kvm/kvmi_msg.c
@@ -12,6 +12,7 @@ static const char *const msg_IDs[] = {
 	[KVMI_CHECK_COMMAND]         = "KVMI_CHECK_COMMAND",
 	[KVMI_CHECK_EVENT]           = "KVMI_CHECK_EVENT",
 	[KVMI_CONTROL_CMD_RESPONSE]  = "KVMI_CONTROL_CMD_RESPONSE",
+	[KVMI_GET_GUEST_INFO]        = "KVMI_GET_GUEST_INFO",
 	[KVMI_GET_VERSION]           = "KVMI_GET_VERSION",
 };
 
@@ -213,6 +214,18 @@ static int handle_check_event(struct kvmi *ikvm,
 	return kvmi_msg_vm_maybe_reply(ikvm, msg, ec, NULL, 0);
 }
 
+static int handle_get_guest_info(struct kvmi *ikvm,
+				 const struct kvmi_msg_hdr *msg,
+				 const void *req)
+{
+	struct kvmi_get_guest_info_reply rpl;
+
+	memset(&rpl, 0, sizeof(rpl));
+	rpl.vcpu_count = atomic_read(&ikvm->kvm->online_vcpus);
+
+	return kvmi_msg_vm_maybe_reply(ikvm, msg, 0, &rpl, sizeof(rpl));
+}
+
 static int handle_control_cmd_response(struct kvmi *ikvm,
 					const struct kvmi_msg_hdr *msg,
 					const void *_req)
@@ -246,6 +259,7 @@ static int(*const msg_vm[])(struct kvmi *, const struct kvmi_msg_hdr *,
 	[KVMI_CHECK_COMMAND]         = handle_check_command,
 	[KVMI_CHECK_EVENT]           = handle_check_event,
 	[KVMI_CONTROL_CMD_RESPONSE]  = handle_control_cmd_response,
+	[KVMI_GET_GUEST_INFO]        = handle_get_guest_info,
 	[KVMI_GET_VERSION]           = handle_get_version,
 };