Re: [PATCH v2 7/7] vhost: Add new UAPI to support change to task mode

[Cindy Lu]

On Tue, 15 Oct 2024 at 04:56, Mike Christie <michael.christie@xxxxxxxxxx> wrote:
>
> On 10/3/24 8:58 PM, Cindy Lu wrote:
> > Add a new UAPI to support setting the vhost device to
> > use task mode. The user space application needs to use
> > VHOST_SET_INHERIT_FROM_OWNER to set the mode.
> > This setting must be set before VHOST_SET_OWNER is set.
> >
> > Signed-off-by: Cindy Lu <lulu@xxxxxxxxxx>
> > ---
> >  drivers/vhost/vhost.c      | 18 +++++++++++++++++-
> >  include/uapi/linux/vhost.h |  2 ++
> >  2 files changed, 19 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index 08c9e77916ca..0e5c81026acd 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -2341,8 +2341,24 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
> >  {
> >       struct eventfd_ctx *ctx;
> >       u64 p;
> > -     long r;
> > +     long r = 0;
> >       int i, fd;
> > +     bool inherit_owner;
> > +
> > +     if (ioctl == VHOST_SET_INHERIT_FROM_OWNER) {
>
> Maybe instead of a modparam and this ioctl we just want a new ioctl:
>
> /*
>  * This will setup the owner based on the calling thread instead of
>  * using kthread.
>  */
> #define VHOST_INHERIT_OWNER _IO(VHOST_VIRTIO, 0x83)
>
> It would initially be used by vhost-scsi when worker_per_virtqueue=true
> since that is a new use case and there will be no regressions.
>
> For the other cases we default to VHOST_SET_OWNER. Other QEMU cases or
> tool XYZ can use the new ioctl when they are ready.
>
If I understand correctly, this means the default vhost function is
using kthread?
Thanks
Cindy