Subject: Re: [PATCH v5 0/6] vhost: Add support of kthread API

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 8 Jan 2025 07:23:08 -0500

On Mon, Dec 30, 2024 at 08:43:47PM +0800, Cindy Lu 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.  

I briefly applied this, but there seem to be a bit too
many nits. So I will wait for v6 with everything addressed.

Thanks!

> 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.
>  
> Tested with QEMU with kthread mode/task mode/kthread+task mode
> 
> Cindy Lu (6):
>   vhost: Add a new parameter in vhost_dev to allow user select kthread
>   vhost: Add the vhost_worker to support kthread
>   vhost: Add the cgroup related function
>   vhost: Add worker related functions to support kthread
>   vhost: Add new UAPI to support change to task mode
>   vhost_scsi: Add check for inherit_owner status
> 
>  drivers/vhost/scsi.c       |   8 ++
>  drivers/vhost/vhost.c      | 178 +++++++++++++++++++++++++++++++++----
>  drivers/vhost/vhost.h      |   4 +
>  include/uapi/linux/vhost.h |  19 ++++
>  4 files changed, 192 insertions(+), 17 deletions(-)
> 
> -- 
> 2.45.0