From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751638AbZH0LVo (ORCPT ); Thu, 27 Aug 2009 07:21:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751229AbZH0LVo (ORCPT ); Thu, 27 Aug 2009 07:21:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12122 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750920AbZH0LVn (ORCPT ); Thu, 27 Aug 2009 07:21:43 -0400 Date: Thu, 27 Aug 2009 14:19:48 +0300 From: "Michael S. Tsirkin" To: Rusty Russell Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@elte.hu, linux-mm@kvack.org, akpm@linux-foundation.org, hpa@zytor.com, gregory.haskins@gmail.com Subject: Re: [PATCHv4 2/2] vhost_net: a kernel-level virtio server Message-ID: <20090827111947.GA21801@redhat.com> References: <200908252140.41295.rusty@rustcorp.com.au> <20090827104517.GB8545@redhat.com> <200908272040.02628.rusty@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200908272040.02628.rusty@rustcorp.com.au> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 27, 2009 at 08:40:02PM +0930, Rusty Russell wrote: > 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 :) Okay, writes are ordered them. But mb() orders reads as well, so it'll have to have a real one IMO, even in userspace? > The kernel uses a real insn if XMM/XMM2, but I don't > know if userspace needs that. I just use compiler barriers. > > Thanks, > Rusty.