[PATCH] qemu: modprobe vhost-vsock module

[Stefano Garzarella]

On Tue, Jul 28, 2020 at 12:58:07PM +0300, Nikolay Shirokovskiy wrote:
> /dev/vhost-vsock is usable only if the module is loaded.  Let's load the module
> just like in other places where kernel module is required (nbd, pci stub
> driver).

Just a note, starting from Linux 4.13 (f4660cc994e1 ("vhost/vsock: use static
minor number")) the kernel module should be automatically loaded when an
application try to open /dev/vhost-vsock.

Did you find a case where that doesn't happen?

Thanks,
Stefano

> 
> Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy at virtuozzo.com>
> ---
>  src/qemu/qemu_process.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
> index ec6ca14..5aaa77c 100644
> --- a/src/qemu/qemu_process.c
> +++ b/src/qemu/qemu_process.c
> @@ -92,6 +92,7 @@
>  #include "viridentity.h"
>  #include "virthreadjob.h"
>  #include "virutil.h"
> +#include "virkmod.h"
>  
>  #define VIR_FROM_THIS VIR_FROM_QEMU
>  
> @@ -6414,6 +6415,7 @@ qemuProcessPrepareHostStorage(virQEMUDriverPtr driver,
>      return 0;
>  }
>  
> +#define VHOST_VSOCK_MODULE "vhost-vsock"
>  
>  int
>  qemuProcessOpenVhostVsock(virDomainVsockDefPtr vsock)
> @@ -6422,6 +6424,22 @@ qemuProcessOpenVhostVsock(virDomainVsockDefPtr vsock)
>      const char *vsock_path = "/dev/vhost-vsock";
>      int fd;
>  
> +    if (virKModIsProhibited(VHOST_VSOCK_MODULE)) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                       _("Failed to load vhost-vsock module: "
> +                         "administratively prohibited"));
> +        return -1;
> +    } else {
> +        g_autofree char *errbuf = NULL;
> +
> +        if ((errbuf = virKModLoad(VHOST_VSOCK_MODULE))) {
> +            virReportError(VIR_ERR_INTERNAL_ERROR,
> +                           _("Failed to load vhost-vsock module: %s"),
> +                           errbuf);
> +            return -1;
> +        }
> +    }
> +
>      if ((fd = open(vsock_path, O_RDWR)) < 0) {
>          virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>                         "%s", _("unable to open vhost-vsock device"));
> -- 
> 1.8.3.1
>