Re: [PATCHv4 2/2] vhost_net: a kernel-level virtio server

From: Rusty Russell
Date: Thu Aug 27 2009 - 07:10:19 EST

On Thu, 27 Aug 2009 08:15:18 pm Michael S. Tsirkin wrote:
> On Tue, Aug 25, 2009 at 09:40:40PM +0930, Rusty Russell wrote:
> > Also, see other fixes to the lguest launcher since then which might
> > be relevant to this code:
> > lguest: get more serious about wmb() in example Launcher code
> Heh, this just gets one step closer to a real wmb. I just used the
> correct code from linux, so I think nothing needs to be done in vhost.
> Apropos this change in lguest: why is a compiler barrier sufficient? The
> comment says devices are run in separate threads (presumably from
> guest?), if so don't you need to tell CPU that there's a barrier as
> well?

Yep, but x86 only :) The kernel uses a real insn if XMM/XMM2, but I don't
know if userspace needs that. I just use compiler barriers.

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