These commands can be used by the introspection tool to check what
introspection commands and events are supported (by KVMi) and allowed
(by userspace/QEMU).
The introspection tool will get one of the following error codes:
* -KVM_EOPNOTSUPP (unsupported command/event)
* -KVM_PERM (disallowed command/event)
* -KVM_EINVAL (the padding space, used for future extensions,
is not zero)
* 0 (the command/event is supported and allowed)
These commands can be seen as an alternative method to KVMI_GET_VERSION
in checking if the introspection supports a specific command/event.
As with the KVMI_GET_VERSION command, these commands can never be
disallowed by userspace/QEMU.
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
Documentation/virtual/kvm/kvmi.rst | 60 ++++++++++++++++++++++++++++++
include/uapi/linux/kvmi.h | 12 ++++++
virt/kvm/kvmi.c | 8 +++-
virt/kvm/kvmi_msg.c | 38 +++++++++++++++++++
4 files changed, 117 insertions(+), 1 deletion(-)
diff --git a/Documentation/virtual/kvm/kvmi.rst b/Documentation/virtual/kvm/kvmi.rst
index 82de474d512b..61cf69aa5d07 100644
--- a/Documentation/virtual/kvm/kvmi.rst
+++ b/Documentation/virtual/kvm/kvmi.rst
@@ -302,3 +302,63 @@ While the command reply is disabled:
* the reply status is ignored for any unsupported/unknown or disallowed
commands (and ``struct kvmi_error_code`` will be sent with -KVM_EOPNOTSUPP
or -KVM_PERM).
+
+3. KVMI_CHECK_COMMAND
+---------------------
+
+:Architectures: all
+:Versions: >= 1
+:Parameters:
+
+::
+
+ struct kvmi_check_command {
+ __u16 id;
+ __u16 padding1;
+ __u32 padding2;
+ };
+
+:Returns:
+
+::
+
+ struct kvmi_error_code;
+
+Checks if the command specified by ``id`` is allowed.
+
+This command is always allowed.
+
+:Errors:
+
+* -KVM_PERM - the command specified by ``id`` is disallowed
+* -KVM_EINVAL - padding is not zero
+
+4. KVMI_CHECK_EVENT
+-------------------
+
+:Architectures: all
+:Versions: >= 1
+:Parameters:
+
+::
+
+ struct kvmi_check_event {
+ __u16 id;
+ __u16 padding1;
+ __u32 padding2;
+ };
+
+:Returns:
+
+::
+
+ struct kvmi_error_code;
+
+Checks if the event specified by ``id`` is allowed.
+
+This command is always allowed.
+
+:Errors:
+
+* -KVM_PERM - the event specified by ``id`` is disallowed
+* -KVM_EINVAL - padding is not zero
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index a1ab39c5b8e0..7390303371c9 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -90,4 +90,16 @@ struct kvmi_control_cmd_response {
__u32 padding2;
};
+struct kvmi_check_command {
+ __u16 id;
+ __u16 padding1;
+ __u32 padding2;
+};
+
+struct kvmi_check_event {
+ __u16 id;
+ __u16 padding1;
+ __u32 padding2;
+};
+
#endif /* _UAPI__LINUX_KVMI_H */
diff --git a/virt/kvm/kvmi.c b/virt/kvm/kvmi.c
index d5b6af21564e..dc1bb8326763 100644
--- a/virt/kvm/kvmi.c
+++ b/virt/kvm/kvmi.c
@@ -69,6 +69,8 @@ static bool alloc_kvmi(struct kvm *kvm, const struct kvm_introspection *qemu)
return false;
set_bit(KVMI_GET_VERSION, ikvm->cmd_allow_mask);
+ set_bit(KVMI_CHECK_COMMAND, ikvm->cmd_allow_mask);
+ set_bit(KVMI_CHECK_EVENT, ikvm->cmd_allow_mask);
memcpy(&ikvm->uuid, &qemu->uuid, sizeof(ikvm->uuid));
@@ -295,10 +297,14 @@ int kvmi_ioctl_command(struct kvm *kvm, void __user *argp)
if (!allow) {
DECLARE_BITMAP(always_allowed, KVMI_NUM_COMMANDS);
- if (id == KVMI_GET_VERSION)
+ if (id == KVMI_GET_VERSION
+ || id == KVMI_CHECK_COMMAND
+ || id == KVMI_CHECK_EVENT)
return -EPERM;
set_bit(KVMI_GET_VERSION, always_allowed);
+ set_bit(KVMI_CHECK_COMMAND, always_allowed);
+ set_bit(KVMI_CHECK_EVENT, always_allowed);
bitmap_andnot(requested, requested, always_allowed,
KVMI_NUM_COMMANDS);
diff --git a/virt/kvm/kvmi_msg.c b/virt/kvm/kvmi_msg.c
index 2237a6ed25f6..e24996611e3a 100644
--- a/virt/kvm/kvmi_msg.c
+++ b/virt/kvm/kvmi_msg.c
@@ -9,6 +9,8 @@
#include "kvmi_int.h"
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_VERSION] = "KVMI_GET_VERSION",
};
@@ -177,6 +179,40 @@ static bool is_command_allowed(struct kvmi *ikvm, int id)
return test_bit(id, ikvm->cmd_allow_mask);
}
+static int handle_check_command(struct kvmi *ikvm,
+ const struct kvmi_msg_hdr *msg,
+ const void *_req)
+{
+ const struct kvmi_check_command *req = _req;
+ int ec = 0;
+
+ if (req->padding1 || req->padding2)
+ ec = -KVM_EINVAL;
+ else if (!is_command_allowed(ikvm, req->id))
+ ec = -KVM_EPERM;
+
+ return kvmi_msg_vm_maybe_reply(ikvm, msg, ec, NULL, 0);
+}
+
+static bool is_event_allowed(struct kvmi *ikvm, int id)
+{
+ return test_bit(id, ikvm->event_allow_mask);
+}
+
+static int handle_check_event(struct kvmi *ikvm,
+ const struct kvmi_msg_hdr *msg, const void *_req)
+{
+ const struct kvmi_check_event *req = _req;
+ int ec = 0;
+
+ if (req->padding1 || req->padding2)
+ ec = -KVM_EINVAL;
+ else if (!is_event_allowed(ikvm, req->id))
+ ec = -KVM_EPERM;
+
+ return kvmi_msg_vm_maybe_reply(ikvm, msg, ec, NULL, 0);
+}
+
static int handle_control_cmd_response(struct kvmi *ikvm,
const struct kvmi_msg_hdr *msg,
const void *_req)
@@ -207,6 +243,8 @@ static int handle_control_cmd_response(struct kvmi *ikvm,
*/
static int(*const msg_vm[])(struct kvmi *, const struct kvmi_msg_hdr *,
const void *) = {
+ [KVMI_CHECK_COMMAND] = handle_check_command,
+ [KVMI_CHECK_EVENT] = handle_check_event,
[KVMI_CONTROL_CMD_RESPONSE] = handle_control_cmd_response,
[KVMI_GET_VERSION] = handle_get_version,
};
