linux-kernel - Re: [RFC V1 07/13] vhost-vdpa: flush workers on suspend

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Date: Fri, 12 Jan 2024 10:28:19 +0800
From: Jason Wang <jasowang@...hat.com>
To: Mike Christie <michael.christie@...cle.com>
Cc: Steve Sistare <steven.sistare@...cle.com>, virtualization@...ts.linux-foundation.org, 
	linux-kernel@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>, 
	Si-Wei Liu <si-wei.liu@...cle.com>, Eugenio Perez Martin <eperezma@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Dragos Tatulea <dtatulea@...dia.com>, 
	Eli Cohen <elic@...dia.com>, Xie Yongji <xieyongji@...edance.com>
Subject: Re: [RFC V1 07/13] vhost-vdpa: flush workers on suspend

On Fri, Jan 12, 2024 at 12:18 AM Mike Christie
<michael.christie@...cle.com> wrote:
>
> On 1/10/24 9:09 PM, Jason Wang wrote:
> > On Thu, Jan 11, 2024 at 4:40 AM Steve Sistare <steven.sistare@...cle.com> wrote:
> >>
> >> To pass ownership of a live vdpa device to a new process, the user
> >> suspends the device, calls VHOST_NEW_OWNER to change the mm, and calls
> >> VHOST_IOTLB_REMAP to change the user virtual addresses to match the new
> >> mm.  Flush workers in suspend to guarantee that no worker sees the new
> >> mm and old VA in between.
> >>
> >> Signed-off-by: Steve Sistare <steven.sistare@...cle.com>
> >> ---
> >>  drivers/vhost/vdpa.c | 4 ++++
> >>  1 file changed, 4 insertions(+)
> >>
> >> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> >> index 8fe1562d24af..9673e8e20d11 100644
> >> --- a/drivers/vhost/vdpa.c
> >> +++ b/drivers/vhost/vdpa.c
> >> @@ -591,10 +591,14 @@ static long vhost_vdpa_suspend(struct vhost_vdpa *v)
> >>  {
> >>         struct vdpa_device *vdpa = v->vdpa;
> >>         const struct vdpa_config_ops *ops = vdpa->config;
> >> +       struct vhost_dev *vdev = &v->vdev;
> >>
> >>         if (!ops->suspend)
> >>                 return -EOPNOTSUPP;
> >>
> >> +       if (vdev->use_worker)
> >> +               vhost_dev_flush(vdev);
> >
> > It looks to me like it's better to check use_woker in vhost_dev_flush.
> >
>
> You can now just call vhost_dev_flush and it will do the right thing.
> The xa_for_each loop will only flush workers if they have been setup,
> so for vdpa it will not find/flush anything.

Right.

Thanks

>
>
>