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

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Date:   Thu, 3 Jun 2021 10:30:46 +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] vdpa/mlx5: Clear vq ready indication upon device reset

On Thu, Jun 03, 2021 at 03:06:31PM +0800, Jason Wang wrote:
> 
> 在 2021/6/3 下午3:00, Jason Wang 写道:
> > 
> > 在 2021/6/2 下午4:59, 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>
> > 
> > 
> > Acked-by: Jason Wang <jasowang@...hat.com>
> 
> 
> A second thought.
> 
> destroy_virtqueue() could be called many places.
> 
> One of them is the mlx5_vdpa_change_map(), if this is case, this looks
> wrong.

Right, although most likely VQs become ready only after all map changes
occur becuase I did not encounter any issue while testing.
> 
> It looks to me it's simpler to do this in clear_virtqueues() which can only
> be called during reset.

There is no clear_virtqueues() function. You probably mean to insert a
call in mlx5_vdpa_set_status() in case it performs reset. This function
will go over all virtqueues and clear their ready flag.

Alternatively we can add boolean argument to teardown_driver() that
signifies if we are in reset flow and in this case we clear ready.

> 
> Thanks
> 
> 
> > 
> > 
> > > ---
> > >   drivers/vdpa/mlx5/net/mlx5_vnet.c | 1 +
> > >   1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > index 02a05492204c..e8bc0842b44c 100644
> > > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > > @@ -862,6 +862,7 @@ static void destroy_virtqueue(struct
> > > mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtq
> > >           return;
> > >       }
> > >       umems_destroy(ndev, mvq);
> > > +    mvq->ready = false;
> > >   }
> > >     static u32 get_rqpn(struct mlx5_vdpa_virtqueue *mvq, bool fw)
>