linux-kernel - Re: [PATCH 2/2] vhost: disentangle vring endianness stuff from the core code

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Message-ID: <20160210144042.49d5fe84@bahia.huguette.org>
Date:	Wed, 10 Feb 2016 14:40:42 +0100
From:	Greg Kurz <gkurz@...ux.vnet.ibm.com>
To:	Cornelia Huck <cornelia.huck@...ibm.com>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 2/2] vhost: disentangle vring endianness stuff from the
 core code

On Wed, 10 Feb 2016 14:23:33 +0100
Cornelia Huck <cornelia.huck@...ibm.com> wrote:

> On Wed, 10 Feb 2016 14:08:43 +0100
> Greg Kurz <gkurz@...ux.vnet.ibm.com> wrote:
> 
> > But you are right, there is a bug: we should rollback if vhost_init_used()
> > fails. Something like below:
> > 
> >  err_used:
> >         vq->private_data = oldsock;
> >         vhost_net_enable_vq(n, vq);
> > +       vhost_adjust_vring_endian(vq);  
> 
> Shouldn't we switch back before we reenable? Or have I lost myself in
> this maze here again?
> 

I haven't spotted any path under vhost_net_enable_vq() that needs
the vring endianness, but indeed it looks safer to switch back
before a worker thread may be woken up.

> >         if (ubufs)
> >                 vhost_net_ubuf_put_wait_and_free(ubufs);
> >  err_ubufs: