Re: [PATCH v12 1/1] vhost: Reintroduces support of kthread API and adds mode selection

[Cindy Lu <lulu@redhat.com>]

On Thu, Jun 19, 2025 at 9:02 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Wed, Jun 18, 2025 at 8:06 PM Nicolas Dichtel
> <nicolas.dichtel@6wind.com> wrote:
> >
> > Le 16/06/2025 à 08:28, Cindy Lu a écrit :
> > > This patch reintroduces kthread mode for vhost workers and provides
> > > configuration to select between kthread and task worker.
> > >
> > > - Add 'fork_owner' parameter to vhost_dev to let users select kthread
> > >   or task mode. Default mode is task mode(VHOST_FORK_OWNER_TASK).
> > >
> > > - Reintroduce kthread mode support:
> > >   * Bring back the original vhost_worker() implementation,
> > >     and renamed to vhost_run_work_kthread_list().
> > >   * Add cgroup support for the kthread
> > >   * Introduce struct vhost_worker_ops:
> > >     - Encapsulates create / stop / wake‑up callbacks.
> > >     - vhost_worker_create() selects the proper ops according to
> > >       inherit_owner.
> > >
> > > - Userspace configuration interface:
> > >   * New IOCTLs:
> > >       - VHOST_SET_FORK_FROM_OWNER lets userspace select task mode
> > >         (VHOST_FORK_OWNER_TASK) or kthread mode (VHOST_FORK_OWNER_KTHREAD)
> > >       - VHOST_GET_FORK_FROM_OWNER reads the current worker mode
> > >   * Expose module parameter 'fork_from_owner_default' to allow system
> > >     administrators to configure the default mode for vhost workers
> > >   * Kconfig option CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL controls whether
> > >     these IOCTLs and the parameter are available (for distros that may
> > >     want to disable them)
> > >
> > > - The VHOST_NEW_WORKER functionality requires fork_owner to be set
> > >   to true, with validation added to ensure proper configuration
> > >
> > > This partially reverts or improves upon:
> > >   commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")
> > >   commit 1cdaafa1b8b4 ("vhost: replace single worker pointer with xarray")
> > >
> > > Signed-off-by: Cindy Lu <lulu@redhat.com>
> > > ---
> > >  drivers/vhost/Kconfig      |  17 +++
> > >  drivers/vhost/vhost.c      | 244 ++++++++++++++++++++++++++++++++++---
> > >  drivers/vhost/vhost.h      |  22 ++++
> > >  include/uapi/linux/vhost.h |  29 +++++
> > >  4 files changed, 294 insertions(+), 18 deletions(-)
> > >
> > > diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
> > > index 020d4fbb947c..1b3602b1f8e2 100644
> > > --- a/drivers/vhost/Kconfig
> > > +++ b/drivers/vhost/Kconfig
> > > @@ -95,4 +95,21 @@ config VHOST_CROSS_ENDIAN_LEGACY
> > >
> > >         If unsure, say "N".
> > >
> > > +config VHOST_ENABLE_FORK_OWNER_CONTROL
> > > +     bool "Enable VHOST_ENABLE_FORK_OWNER_CONTROL"
> > > +     default n
> > Why disabling this option by default?
>
> I think we should enable this by default.
>
> Thanks
>
Thanks jason,  I will send  a new version
Thanks
cindy
> >
> > Regards,
> > Nicolas
> >
>