This command is used to identify the commands/events supported
by the introspection subsystem and it is always allowed.
Any attempt from userspace to explicitly disallow this command through
the KVM_INTROSPECTION_COMMAND ioctl will get -EPERM, unless userspace
disables all commands, using id=-1, in which case KVMI_GET_VERSION is
silently allowed, without error.
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
Documentation/virt/kvm/kvmi.rst | 35 +++++++++++++++++++
include/uapi/linux/kvmi.h | 10 ++++++
.../testing/selftests/kvm/x86_64/kvmi_test.c | 25 +++++++++++++
virt/kvm/introspection/kvmi.c | 27 +++++++++++---
virt/kvm/introspection/kvmi_msg.c | 12 +++++++
5 files changed, 105 insertions(+), 4 deletions(-)
diff --git a/Documentation/virt/kvm/kvmi.rst b/Documentation/virt/kvm/kvmi.rst
index efde4b771586..d848e56f42e9 100644
--- a/Documentation/virt/kvm/kvmi.rst
+++ b/Documentation/virt/kvm/kvmi.rst
@@ -223,3 +223,38 @@ device-specific memory (DMA, emulated MMIO, reserved by a passthrough
device etc.). It is up to the user to determine, using the guest operating
system data structures, the areas that are safe to access (code, stack, heap
etc.).
+
+Commands
+--------
+
+The following C structures are meant to be used directly when communicating
+over the wire. The peer that detects any size mismatch should simply close
+the connection and report the error.
+
+1. KVMI_GET_VERSION
+-------------------
+
+:Architectures: all
+:Versions: >= 1
+:Parameters: none
+:Returns:
+
+::
+
+ struct kvmi_error_code;
+ struct kvmi_get_version_reply {
+ __u32 version;
+ __u32 padding;
+ };
+
+Returns the introspection API version.
+
+This command is always allowed and successful (if the introspection is
+built in kernel).
+
+The userspace should use this command to identify the commands/events
+supported by the kernel side and what messages must be used for event
+replies. These messages might be extended in futures versions and while
+the kernel will accept shorter messages (older versions) or bigger
+messages (newer versions, ignoring the extra information) it will not
+accept bigger/newer event replies.
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index 6fdaa92393a4..b0a5b72d3936 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -6,11 +6,16 @@
* KVMI structures and definitions
*/
+#include <linux/kernel.h>
+#include <linux/types.h>
+
enum {
KVMI_VERSION = 0x00000001
};
enum {
+ KVMI_GET_VERSION = 2,
+
KVMI_NUM_MESSAGES
};
@@ -40,4 +45,9 @@ struct kvmi_error_code {
__u32 padding;
};
+struct kvmi_get_version_reply {
+ __u32 version;
+ __u32 padding;
+};
+
#endif /* _UAPI__LINUX_KVMI_H */
diff --git a/tools/testing/selftests/kvm/x86_64/kvmi_test.c b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
index 4c1fe67c8e35..327272e266ff 100644
--- a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
@@ -177,12 +177,37 @@ static void test_cmd_invalid(void)
-r, kvm_strerror(-r));
}
+static void test_vm_command(int cmd_id, struct kvmi_msg_hdr *req,
+ size_t req_size, void *rpl, size_t rpl_size)
+{
+ int r;
+
+ r = do_command(cmd_id, req, req_size, rpl, rpl_size);
+ TEST_ASSERT(r == 0,
+ "Command %d failed, error %d (%s)\n",
+ cmd_id, -r, kvm_strerror(-r));
+}
+
+static void test_cmd_get_version(void)
+{
+ struct kvmi_get_version_reply rpl;
+ struct kvmi_msg_hdr req;
+
+ test_vm_command(KVMI_GET_VERSION, &req, sizeof(req), &rpl, sizeof(rpl));
+ TEST_ASSERT(rpl.version == KVMI_VERSION,
+ "Unexpected KVMI version %d, expecting %d\n",
+ rpl.version, KVMI_VERSION);
+
+ DEBUG("KVMI version: %u\n", rpl.version);
+}
+
static void test_introspection(struct kvm_vm *vm)
{
setup_socket();
hook_introspection(vm);
test_cmd_invalid();
+ test_cmd_get_version();
unhook_introspection(vm);
}
diff --git a/virt/kvm/introspection/kvmi.c b/virt/kvm/introspection/kvmi.c
index 88d29408fbf1..8cd66b1dac02 100644
--- a/virt/kvm/introspection/kvmi.c
+++ b/virt/kvm/introspection/kvmi.c
@@ -10,6 +10,8 @@
#define KVMI_MSG_SIZE_ALLOC (sizeof(struct kvmi_msg_hdr) + KVMI_MSG_SIZE)
+static DECLARE_BITMAP(Kvmi_always_allowed_commands, KVMI_NUM_COMMANDS);
+
static struct kmem_cache *msg_cache;
void *kvmi_msg_alloc(void)
@@ -43,8 +45,16 @@ static int kvmi_cache_create(void)
return 0;
}
+static void setup_always_allowed_commands(void)
+{
+ bitmap_zero(Kvmi_always_allowed_commands, KVMI_NUM_COMMANDS);
+ set_bit(KVMI_GET_VERSION, Kvmi_always_allowed_commands);
+}
+
int kvmi_init(void)
{
+ setup_always_allowed_commands();
+
return kvmi_cache_create();
}
@@ -71,6 +81,9 @@ alloc_kvmi(struct kvm *kvm, const struct kvm_introspection_hook *hook)
BUILD_BUG_ON(sizeof(hook->uuid) != sizeof(kvmi->uuid));
memcpy(&kvmi->uuid, &hook->uuid, sizeof(kvmi->uuid));
+ bitmap_copy(kvmi->cmd_allow_mask, Kvmi_always_allowed_commands,
+ KVMI_NUM_COMMANDS);
+
kvmi->kvm = kvm;
return kvmi;
@@ -282,8 +295,8 @@ int kvmi_ioctl_event(struct kvm *kvm, void __user *argp)
return err;
}
-static void kvmi_control_allowed_commands(struct kvm_introspection *kvmi,
- int id, bool allow)
+static int kvmi_control_allowed_commands(struct kvm_introspection *kvmi,
+ int id, bool allow)
{
int all_commands = -1;
@@ -294,10 +307,16 @@ static void kvmi_control_allowed_commands(struct kvm_introspection *kvmi,
set_bit(id, kvmi->cmd_allow_mask);
} else {
if (id == all_commands)
- bitmap_zero(kvmi->cmd_allow_mask, KVMI_NUM_COMMANDS);
+ bitmap_copy(kvmi->cmd_allow_mask,
+ Kvmi_always_allowed_commands,
+ KVMI_NUM_COMMANDS);
+ else if (test_bit(id, Kvmi_always_allowed_commands))
+ return -EPERM;
else
clear_bit(id, kvmi->cmd_allow_mask);
}
+
+ return 0;
}
int kvmi_ioctl_command(struct kvm *kvm, void __user *argp)
@@ -314,7 +333,7 @@ int kvmi_ioctl_command(struct kvm *kvm, void __user *argp)
kvmi = KVMI(kvm);
if (kvmi)
- kvmi_control_allowed_commands(kvmi, id, allow);
+ err = kvmi_control_allowed_commands(kvmi, id, allow);
else
err = -EFAULT;
diff --git a/virt/kvm/introspection/kvmi_msg.c b/virt/kvm/introspection/kvmi_msg.c
index 02fc5d95fef6..9efcd896f0c6 100644
--- a/virt/kvm/introspection/kvmi_msg.c
+++ b/virt/kvm/introspection/kvmi_msg.c
@@ -103,11 +103,23 @@ static bool is_command_allowed(struct kvm_introspection *kvmi, u16 id)
return id < KVMI_NUM_COMMANDS && test_bit(id, kvmi->cmd_allow_mask);
}
+static int handle_get_version(struct kvm_introspection *kvmi,
+ const struct kvmi_msg_hdr *msg, const void *req)
+{
+ struct kvmi_get_version_reply rpl;
+
+ memset(&rpl, 0, sizeof(rpl));
+ rpl.version = KVMI_VERSION;
+
+ return kvmi_msg_vm_reply(kvmi, msg, 0, &rpl, sizeof(rpl));
+}
+
/*
* These commands are executed by the receiving thread/worker.
*/
static int(*const msg_vm[])(struct kvm_introspection *,
const struct kvmi_msg_hdr *, const void *) = {
+ [KVMI_GET_VERSION] = handle_get_version,
};
static bool is_vm_command(u16 id)
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