From: Mark McLoughlin <markmc@redhat.com>
To: Alex Williamson <alex.williamson@hp.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>, kvm <kvm@vger.kernel.org>,
netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH 2/4] virtio_net: Add a virtqueue for outbound control commands
Date: Wed, 14 Jan 2009 16:37:06 +0000 [thread overview]
Message-ID: <1231951026.4944.304.camel@localhost.localdomain> (raw)
In-Reply-To: <1231948868.7109.288.camel@lappy>
On Wed, 2009-01-14 at 09:01 -0700, Alex Williamson wrote:
> On Wed, 2009-01-14 at 10:15 +0000, Mark McLoughlin wrote:
> > On Tue, 2009-01-13 at 14:23 -0700, Alex Williamson wrote:
> > > +static int virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
> > > + void *data, unsigned int len)
> > > +{
> > > + struct scatterlist sg[3];
> > > + struct {
> > > + u8 class;
> > > + u8 cmd;
> > > + } ctrl_cmd;
> >
> > I'd like to see this defined in virtio_net_hdr.
>
> As part of struct virtio_net_hdr? I'm not sure what that'd buy us and
> would likely break compatibility. Or do you simply mean defined in
> virtio-net.h?
Yep, sorry, I meant virtio-net.h
> > > + u8 ctrl_status;
> > > + unsigned int tmp;
> > > + int i = 0;
> > > +
> > > + if (!vi->cvq)
> > > + return -EFAULT;
> >
> > BUG_ON() probably makes more sense here.
>
> This is to allow a newer virtio_net guest driver to run on an old qemu.
> That's why I don't generate a fatal error if we don't find the control
> queue. In that case the backend will be running in promiscuous mode and
> I think all of these commands can safely fail. Thanks for the comments.
Yep, but what I mean is that virtio_net_send_command() should never be
called if the host doesn't have send queue support - i.e. force the
calling code to think about what should be done on older hosts.
Cheers,
Mark.
prev parent reply other threads:[~2009-01-14 16:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-13 21:23 [PATCH 2/4] virtio_net: Add a virtqueue for outbound control commands Alex Williamson
2009-01-14 10:15 ` Mark McLoughlin
2009-01-14 16:01 ` Alex Williamson
2009-01-14 16:37 ` Mark McLoughlin [this message]
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