Subject: Re: [PATCH V6 0/4 net-next] macvtap/vhost TX zero-copy support
From: Shirley Ma <mashirle@us.ibm.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: David Miller <davem@davemloft.net>, Eric Dumazet <eric.dumazet@gmail.com>,
        Avi Kivity <avi@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
        netdev@vger.kernel.org, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Date: Sat, 28 May 2011 11:07:03 -0700
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On Thu, 2011-05-26 at 13:31 -0700, Shirley Ma wrote:
> On Thu, 2011-05-26 at 23:28 +0300, Michael S. Tsirkin wrote:
> > On Thu, May 26, 2011 at 01:00:20PM -0700, Shirley Ma wrote:
> > > 3. Add sleep in vhost shutting down instead of busy-wait for
> > outstanding
> > >    DMAs.
> > 
> > I still think this is not much better. We need to use a
> > completion structure and wait on it instead.
> > If this gets blocked thinkably a tx watchdog can fire and save us
> > from blocking forver :) 
> 
> Ok, I can add a completion structure here. 

The code here doesn't block forever during shutdown, it will release all
outstanding userspace buffers anyway, see vhost_zerocopy_signal_used()
shutdown case.

Thanks
Shirley

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