Re: [PATCH v8 8/8] vhost: Add a KConfig knob to enable IOCTL VHOST_FORK_FROM_OWNER

Cindy Lu
2025-04-09T08:38:26Z

On Tue, Apr 8, 2025 at 7:56 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Fri, Mar 28, 2025 at 06:02:52PM +0800, Cindy Lu wrote:
> > Introduce a new config knob `CONFIG_VHOST_ENABLE_FORK_OWNER_IOCTL`,
> > to control the availability of the `VHOST_FORK_FROM_OWNER` ioctl.
> > When CONFIG_VHOST_ENABLE_FORK_OWNER_IOCTL is set to n, the ioctl
> > is disabled, and any attempt to use it will result in failure.
> >
> > Signed-off-by: Cindy Lu <lulu@redhat.com>
> > ---
> > drivers/vhost/Kconfig | 15 +++++++++++++++
> > drivers/vhost/vhost.c | 3 +++
> > 2 files changed, 18 insertions(+)
> >
> > diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> > index b455d9ab6f3d..e5b9dcbf31b6 100644
> > --- a/drivers/vhost/Kconfig
> > +++ b/drivers/vhost/Kconfig
> > @@ -95,3 +95,18 @@ config VHOST_CROSS_ENDIAN_LEGACY
> > If unsure, say "N".
> >
> > endif
> > +
> > +config VHOST_ENABLE_FORK_OWNER_IOCTL
> > + bool "Enable IOCTL VHOST_FORK_FROM_OWNER"
> > + default n
> > + help
> > + This option enables the IOCTL VHOST_FORK_FROM_OWNER, which allows
> > + userspace applications to modify the thread mode for vhost devices.
>
> ok
>
> > + By default, `CONFIG_VHOST_ENABLE_FORK_OWNER_IOCTL` is set to `n`,
> > + meaning the ioctl is disabled and any operation using this ioctl
> > + will fail.
> > + When the configuration is enabled (y), the ioctl becomes
> > + available, allowing users to set the mode if needed.
>
> no need to be so verbose - the disabled beavious belongs in commit log
> not here.
>
> Also either ioctl or IOCTL but not both.
>
sure, will change this
Thanks
cindy
> > +
> > + If unsure, say "N".
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index fb0c7fb43f78..568e43cb54a9 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -2294,6 +2294,8 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
> > r = vhost_dev_set_owner(d);
> > goto done;
> > }
> > +
> > +#ifdef CONFIG_VHOST_ENABLE_FORK_OWNER_IOCTL
> > if (ioctl == VHOST_FORK_FROM_OWNER) {
> > u8 inherit_owner;
> > /*inherit_owner can only be modified before owner is set*/
> > @@ -2313,6 +2315,7 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
> > r = 0;
> > goto done;
> > }
> > +#endif
> > /* You must be the owner to do anything else */
> > r = vhost_dev_check_owner(d);
> > if (r)
> > --
> > 2.45.0
>