linux-kernel - Re: [PATCH V3 1/3] vhost-vdpa: flush workers on suspend

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Date: Tue, 21 May 2024 09:38:29 -0400
From: Steven Sistare <steven.sistare@...cle.com>
To: Jason Wang <jasowang@...hat.com>
Cc: 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>,
        Xie Yongji <xieyongji@...edance.com>,
        Stefano Garzarella <sgarzare@...hat.com>
Subject: Re: [PATCH V3 1/3] vhost-vdpa: flush workers on suspend

On 5/20/2024 10:28 PM, Jason Wang wrote:
> On Mon, May 20, 2024 at 11:21 PM Steve Sistare
> <steven.sistare@...cle.com> wrote:
>>
>> Flush to guarantee no workers are running when suspend returns.
>>
>> Fixes: f345a0143b4d ("vhost-vdpa: uAPI to suspend the device")
>> Signed-off-by: Steve Sistare <steven.sistare@...cle.com>
>> Acked-by: Eugenio Pérez <eperezma@...hat.com>
>> ---
>>   drivers/vhost/vdpa.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>> index ba52d128aeb7..189596caaec9 100644
>> --- a/drivers/vhost/vdpa.c
>> +++ b/drivers/vhost/vdpa.c
>> @@ -594,6 +594,7 @@ static long vhost_vdpa_suspend(struct vhost_vdpa *v)
>>          struct vdpa_device *vdpa = v->vdpa;
>>          const struct vdpa_config_ops *ops = vdpa->config;
>>          int ret;
>> +       struct vhost_dev *vdev = &v->vdev;
>>
>>          if (!(ops->get_status(vdpa) & VIRTIO_CONFIG_S_DRIVER_OK))
>>                  return 0;
>> @@ -601,6 +602,8 @@ static long vhost_vdpa_suspend(struct vhost_vdpa *v)
>>          if (!ops->suspend)
>>                  return -EOPNOTSUPP;
>>
>> +       vhost_dev_flush(vdev);
> 
> vhost-vDPA doesn't use workers, see:
> 
>          vhost_dev_init(dev, vqs, nvqs, 0, 0, 0, false,
>                         vhost_vdpa_process_iotlb_msg);
> 
> So I wonder if this is a must.

True, but I am adding this to be future proof.  I could instead log a warning
or an error message if vhost_vdpa_suspend is called and v->vdev.use_worker=true,
but IMO we should just fix it, given that the fix is trivial.

- Steve