On Sun, Sep 29, 2024 at 07:35:35PM +0200, Aleksandr Mikhalitsyn wrote:

On Sun, Sep 29, 2024 at 6:56 PM Michael S. Tsirkin [off-list ref] wrote:

quoted

On Thu, Sep 26, 2024 at 06:16:40PM +0200, Alexander Mikhalitsyn wrote:

quoted

Add an explicit MODULE_VERSION("0.0.1") specification
for a vhost_vsock module. It is useful because it allows
userspace to check if vhost_vsock is there when it is
configured as a built-in.

Without this change, there is no /sys/module/vhost_vsock directory.

With this change:
$ ls -la /sys/module/vhost_vsock/
total 0
drwxr-xr-x   2 root root    0 Sep 26 15:59 .
drwxr-xr-x 100 root root    0 Sep 26 15:59 ..
--w-------   1 root root 4096 Sep 26 15:59 uevent
-r--r--r--   1 root root 4096 Sep 26 15:59 version

Signed-off-by: Alexander Mikhalitsyn <redacted>

Dear Michael,

quoted

Why not check that the misc device is registered?

It is possible to read /proc/misc and check if "241 vhost-vsock" is
there, but it means that userspace
needs to have a specific logic for vsock. At the same time, it's quite
convenient to do something like:
    if [ ! -d /sys/modules/vhost_vsock ]; then
        modprobe vhost_vsock
    fi

quoted

I'd rather not add a new UAPI until actually necessary.

I don't insist. I decided to send this patch because, while I was
debugging a non-related kernel issue
on my local dev environment I accidentally discovered that LXD
(containers and VM manager)
fails to run VMs because it fails to load the vhost_vsock module (but
it was built-in in my debug kernel
and the module file didn't exist). Then I discovered that before
trying to load a module we
check if /sys/module/<module name> exists. And found that, for some
reason /sys/module/vhost_vsock
does not exist when vhost_vsock is configured as a built-in, and
/sys/module/vhost_vsock *does* exist when
vhost_vsock is loaded as a module. It looks like an inconsistency and
I also checked that other modules in
drivers/vhost have MODULE_VERSION specified and version is 0.0.1. I
thought that this change looks legitimate
and convenient for userspace consumers.

Kind regards,
Alex

I'll ask you to put this explanation in the commit log,
and I'll pick this up.

quoted

quoted

---
 drivers/vhost/vsock.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 802153e23073..287ea8e480b5 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c

@@ -956,6 +956,7 @@ static void __exit vhost_vsock_exit(void)

 module_init(vhost_vsock_init);
 module_exit(vhost_vsock_exit);
+MODULE_VERSION("0.0.1");
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Asias He");
 MODULE_DESCRIPTION("vhost transport for vsock ");
--

2.34.1