Re: [PATCH v8 6/8] vhost: uapi to control task mode (owner vs kthread)

Cindy Lu
2025-04-07T03:20:14Z

On Tue, Apr 1, 2025 at 9:57 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> On Fri, Mar 28, 2025 at 06:02:50PM +0800, Cindy Lu wrote:
> >Add a new UAPI to configure the vhost device to use the kthread mode
>
> nit: missing . at the end
>
> >The userspace application can use IOCTL VHOST_FORK_FROM_OWNER
> >to choose between owner and kthread mode if necessary
>
> Ditto
>
> >This setting must be applied before VHOST_SET_OWNER, as the worker
> >will be created in the VHOST_SET_OWNER function
>
> Ditto.
>
Sure, will fix this

> >
> >Signed-off-by: Cindy Lu <lulu@redhat.com>
> >---
> > drivers/vhost/vhost.c | 22 ++++++++++++++++++++--
> > include/uapi/linux/vhost.h | 16 ++++++++++++++++
> > 2 files changed, 36 insertions(+), 2 deletions(-)
> >
> >diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> >index be97028a8baf..ff930c2e5b78 100644
> >--- a/drivers/vhost/vhost.c
> >+++ b/drivers/vhost/vhost.c
> >@@ -1134,7 +1134,7 @@ 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.
> >@@ -2287,7 +2287,25 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
> > r = vhost_dev_set_owner(d);
> > goto done;
> > }
> >-
>
> As I mentioned, I'll add the Kconfig in this patch to avoid bisection
> issues.
>
> The rest LGTM.
>
sure, will fix this
Thanks
cindy
> Thanks,
> Stefano
>
> >+ if (ioctl == VHOST_FORK_FROM_OWNER) {
> >+ u8 inherit_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;
> >+ }
> >+ if (inherit_owner > 1) {
> >+ r = -EINVAL;
> >+ goto done;
> >+ }
> >+ d->inherit_owner = (bool)inherit_owner;
> >+ r = 0;
> >+ 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..1ae0917bfeca 100644
> >--- a/include/uapi/linux/vhost.h
> >+++ b/include/uapi/linux/vhost.h
> >@@ -235,4 +235,20 @@
> > */
> > #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,
> >+ * This ioctl must called before VHOST_SET_OWNER.
> >+ *
> >+ * @param inherit_owner: An 8-bit value that determines the vhost thread mode
> >+ *
> >+ * When inherit_owner is set to 1(default value):
> >+ * - Vhost will create tasks similar to processes forked from the owner,
> >+ * inheriting all of the owner's attributes.
> >+ *
> >+ * When inherit_owner is set to 0:
> >+ * - Vhost will create tasks as kernel thread.
> >+ */
> >+#define VHOST_FORK_FROM_OWNER _IOW(VHOST_VIRTIO, 0x83, __u8)
> >+
> > #endif
> >--
> >2.45.0
> >
>