Re: [PATCH v8 0/8] vhost: Add support of kthread API

Lei Yang
2025-03-31T12:00:18Z

QE tested this series of v8 with virtio-net regression tests,
everything works fine.

Tested-by: Lei Yang <leiyang@redhat.com>

On Fri, Mar 28, 2025 at 6:04 PM Cindy Lu <lulu@redhat.com> wrote:
>
> In commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads"),
> the vhost now uses vhost_task and operates as a child of the
> owner thread. This aligns with containerization principles.
> However, this change has caused confusion for some legacy
> userspace applications. Therefore, we are reintroducing
> support for the kthread API.
>
> In this series, a new UAPI is implemented to allow
> userspace applications to configure their thread mode.
>
> Changelog v2:
> 1. Change the module_param's name to enforce_inherit_owner, and the default value is true.
> 2. Change the UAPI's name to VHOST_SET_INHERIT_FROM_OWNER.
>
> Changelog v3:
> 1. Change the module_param's name to inherit_owner_default, and the default value is true.
> 2. Add a structure for task function; the worker will select a different mode based on the value inherit_owner.
> 3. device will have their own inherit_owner in struct vhost_dev
> 4. Address other comments
>
> Changelog v4:
> 1. remove the module_param, only keep the UAPI
> 2. remove the structure for task function; change to use the function pointer in vhost_worker
> 3. fix the issue in vhost_worker_create and vhost_dev_ioctl
> 4. Address other comments
>
> Changelog v5:
> 1. Change wakeup and stop function pointers in struct vhost_worker to void.
> 2. merging patches 4, 5, 6 in a single patch
> 3. Fix spelling issues and address other comments.
>
> Changelog v6:
> 1. move the check of VHOST_NEW_WORKER from vhost_scsi to vhost
> 2. Change the ioctl name VHOST_SET_INHERIT_FROM_OWNER to VHOST_FORK_FROM_OWNER
> 3. reuse the function __vhost_worker_flush
> 4. use a ops sturct to support worker relates function
> 5. reset the value of inherit_owner in vhost_dev_reset_owner.
>
> Changelog v7:
> 1. add a KConfig knob to disable legacy app support
> 2. Split the changes into two patches to separately introduce the ops and add kthread support.
> 3. Utilized INX_MAX to avoid modifications in __vhost_worker_flush
> 4. Rebased on the latest kernel
> 5. Address other comments
>
> Changelog v8:
> 1. Rebased on the latest kernel
> 2. Address some other comments
>
> Tested with QEMU with kthread mode/task mode/kthread+task mode
>
> Cindy Lu (8):
> vhost: Add a new parameter in vhost_dev to allow user select kthread
> vhost: Reintroduce vhost_worker to support kthread
> vhost: Add the cgroup related function
> vhost: Introduce vhost_worker_ops in vhost_worker
> vhost: Reintroduce kthread mode support in vhost
> vhost: uapi to control task mode (owner vs kthread)
> vhost: Add check for inherit_owner status
> vhost: Add a KConfig knob to enable IOCTL VHOST_FORK_FROM_OWNER
>
> drivers/vhost/Kconfig | 15 +++
> drivers/vhost/vhost.c | 219 +++++++++++++++++++++++++++++++++----
> drivers/vhost/vhost.h | 21 ++++
> include/uapi/linux/vhost.h | 16 +++
> 4 files changed, 252 insertions(+), 19 deletions(-)
>
> --
> 2.45.0
>
>