On Tue, Feb 25, 2025 at 5:46 AM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> better subject:
>
> vhost: uapi to control task mode (owner vs kthread)
>
>
> On Sun, Feb 23, 2025 at 11:36:20PM +0800, Cindy Lu wrote:
> > Add a new UAPI to enable setting the vhost device to task mode.
>
> better:
>
> Add a new UAPI to configure the vhost device to use the kthread mode
>
Thanks MST, will change this
>
> > The userspace application can use VHOST_SET_INHERIT_FROM_OWNER
> > to configure the mode
>
> ... to either owner or kthread.
>
sure, will change this
thanks
cindy
>
> > if necessary.
> > This setting must be applied before VHOST_SET_OWNER, as the worker
> > will be created in the VHOST_SET_OWNER function
> >
> > Signed-off-by: Cindy Lu <lulu@xxxxxxxxxx>
> > ---
> > drivers/vhost/vhost.c | 24 ++++++++++++++++++++++--
> > include/uapi/linux/vhost.h | 18 ++++++++++++++++++
> > 2 files changed, 40 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index d8c0ea118bb1..45d8f5c5bca9 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -1133,7 +1133,7 @@ void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_iotlb *umem)
> > int i;
> >
> > vhost_dev_cleanup(dev);
> > -
> > + dev->inherit_owner = true;
> > dev->umem = umem;
> > /* We don't need VQ locks below since vhost_dev_cleanup makes sure
> > * VQs aren't running.
> > @@ -2278,15 +2278,35 @@ 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;
> > + u8 inherit_owner;
> >
> > /* If you are not the owner, you can become one */
> > if (ioctl == VHOST_SET_OWNER) {
> > r = vhost_dev_set_owner(d);
> > goto done;
> > }
> > + if (ioctl == VHOST_FORK_FROM_OWNER) {
> > + /*inherit_owner can only be modified before owner is set*/
> > + if (vhost_dev_has_owner(d)) {
> > + r = -EBUSY;
> > + goto done;
> > + }
> > + if (copy_from_user(&inherit_owner, argp, sizeof(u8))) {
> > + r = -EFAULT;
> > + goto done;
> > + }
> > + /* Validate the inherit_owner value, ensuring it is either 0 or 1 */
> > + if (inherit_owner > 1) {
> > + r = -EINVAL;
> > + goto done;
> > + }
> > +
> > + d->inherit_owner = (bool)inherit_owner;
> >
> > + goto done;
> > + }
> > /* You must be the owner to do anything else */
> > r = vhost_dev_check_owner(d);
> > if (r)
> > diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> > index b95dd84eef2d..8f558b433536 100644
> > --- a/include/uapi/linux/vhost.h
> > +++ b/include/uapi/linux/vhost.h
> > @@ -235,4 +235,22 @@
> > */
> > #define VHOST_VDPA_GET_VRING_SIZE _IOWR(VHOST_VIRTIO, 0x82, \
> > struct vhost_vring_state)
> > +
> > +/**
> > + * VHOST_FORK_FROM_OWNER - Set the inherit_owner flag for the vhost device
> > + *
> > + * @param inherit_owner: An 8-bit value that determines the vhost thread mode
> > + *
> > + * When inherit_owner is set to 1:
> > + * - The VHOST worker threads inherit its values/checks from
> > + * the thread that owns the VHOST device, The vhost threads will
> > + * be counted in the nproc rlimits.
> > + *
> > + * When inherit_owner is set to 0:
> > + * - The VHOST worker threads will use the traditional kernel thread (kthread)
> > + * implementation, which may be preferred by older userspace applications that
> > + * do not utilize the newer vhost_task concept.
> > + */
> > +#define VHOST_FORK_FROM_OWNER _IOW(VHOST_VIRTIO, 0x83, __u8)
> > +
> > #endif
> > --
> > 2.45.0
>
