linux-kernel - Re: [PATCH v1] vdpa/mlx5: Clear vq ready indication upon device reset

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Date:   Sun, 6 Jun 2021 08:04:45 +0300
From:   Eli Cohen <elic@...dia.com>
To:     Jason Wang <jasowang@...hat.com>
CC:     <mst@...hat.com>, <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] vdpa/mlx5: Clear vq ready indication upon device reset

On Fri, Jun 04, 2021 at 10:34:29AM +0800, Jason Wang wrote:
> 
> 在 2021/6/3 下午4:10, Eli Cohen 写道:
> > After device reset, the virtqueues are not ready so clear the ready
> > field.
> > 
> > Failing to do so can result in virtio_vdpa failing to load if the device
> > was previously used by vhost_vdpa and the old values are ready.
> > virtio_vdpa expects to find VQs in "not ready" state.
> > 
> > Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
> > Signed-off-by: Eli Cohen <elic@...dia.com>
> > ---
> > v0 --> v1:
> >    Make sure clear of ready is done only in reset flow
> > 
> >   drivers/vdpa/mlx5/net/mlx5_vnet.c | 9 +++++++++
> >   1 file changed, 9 insertions(+)
> > 
> > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > index 02a05492204c..eaeae67e0ff0 100644
> > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > @@ -1766,6 +1766,14 @@ static void teardown_driver(struct mlx5_vdpa_net *ndev)
> >   	mutex_unlock(&ndev->reslock);
> >   }
> > +static void clear_vqs_ready(struct mlx5_vdpa_net *ndev)
> > +{
> > +	int i;
> > +
> > +	for (i = ndev->mvdev.max_vqs - 1; i >= 0; i--)
> > +		ndev->vqs[i].ready = false;
> 
> 
> The patch looks correct but I wonder the reason for the decreasing used in
> the loop.

No special reason. I just copy pasted it from somewhere else in the
code. Will post another version.
> 
> Usually, it means it has some reason that must be done in that way.
> 
> Thanks
> 
> 
> > +}
> > +
> >   static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
> >   {
> >   	struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> > @@ -1776,6 +1784,7 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
> >   	if (!status) {
> >   		mlx5_vdpa_info(mvdev, "performing device reset\n");
> >   		teardown_driver(ndev);
> > +		clear_vqs_ready(ndev);
> >   		mlx5_vdpa_destroy_mr(&ndev->mvdev);
> >   		ndev->mvdev.status = 0;
> >   		ndev->mvdev.mlx_features = 0;
>