[dpdk-dev] [PATCH] net/virtio: wait device ready in device reset

[Xueming(Steven) Li]

> -----Original Message-----
> From: Andrew Rybchenko <andrew.rybchenko at oktetlabs.ru>
> Sent: Monday, August 23, 2021 5:57 PM
> To: Xueming(Steven) Li <xuemingl at nvidia.com>
> Cc: dev at dpdk.org; Maxime Coquelin <maxime.coquelin at redhat.com>; Chenbo Xia <chenbo.xia at intel.com>
> Subject: Re: [dpdk-dev] [PATCH] net/virtio: wait device ready in device reset
> 
> On 8/23/21 9:39 AM, Xueming Li wrote:
> > According to virtio spec, the device MUST reset when 0 is written to
> > device_status, and present a 0 in device_status once that is done.
> >
> > This patch adds the missing part of waiting status 0 in reset function.
> >
> > Signed-off-by: Xueming Li <xuemingl at nvidia.com>
> > ---
> >  drivers/net/virtio/virtio.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/virtio/virtio.c b/drivers/net/virtio/virtio.c
> > index 7e1e77797f..f003f612d6 100644
> > --- a/drivers/net/virtio/virtio.c
> > +++ b/drivers/net/virtio/virtio.c
> > @@ -3,6 +3,8 @@
> >   * Copyright(c) 2020 Red Hat, Inc.
> >   */
> >
> > +#include <unistd.h>
> > +
> >  #include "virtio.h"
> >
> >  uint64_t
> > @@ -39,8 +41,9 @@ void
> >  virtio_reset(struct virtio_hw *hw)
> >  {
> >  	VIRTIO_OPS(hw)->set_status(hw, VIRTIO_CONFIG_STATUS_RESET);
> > -	/* flush status write */
> > -	VIRTIO_OPS(hw)->get_status(hw);
> > +	/* Flush status write and wait device ready. */
> > +	while (VIRTIO_OPS(hw)->get_status(hw) != VIRTIO_CONFIG_STATUS_RESET)
> > +		usleep(1000L);
> 
> Don't we need a protection against forever loop here?

Good question, ideally we need, kernel driver function vp_reset() seems to have same issue.
How about leaving an error message before return? 

> 
> >  }
> >
> >  void
> >