Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759285AbZIPPXQ (ORCPT ); Wed, 16 Sep 2009 11:23:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759277AbZIPPXO (ORCPT ); Wed, 16 Sep 2009 11:23:14 -0400 Received: from moutng.kundenserver.de ([212.227.126.171]:60668 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759271AbZIPPXN (ORCPT ); Wed, 16 Sep 2009 11:23:13 -0400 From: Arnd Bergmann To: "Michael S. Tsirkin" Subject: Re: [PATCHv5 3/3] vhost_net: a kernel-level virtio server Date: Wed, 16 Sep 2009 17:22:37 +0200 User-Agent: KMail/1.12.1 (Linux/2.6.31-9-generic; KDE/4.3.1; x86_64; ; ) Cc: Gregory Haskins , Avi Kivity , "Ira W. Snyder" , netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@elte.hu, linux-mm@kvack.org, akpm@linux-foundation.org, hpa@zytor.com, Rusty Russell , s.hetze@linux-ag.com, alacrityvm-devel@lists.sourceforge.net References: <20090914164750.GB3745@redhat.com> <200909161657.42628.arnd@arndb.de> <20090916151329.GC5513@redhat.com> In-Reply-To: <20090916151329.GC5513@redhat.com> X-Face: I@=L^?./?$U,EK.)V[4*>`zSqm0>65YtkOe>TFD'!aw?7OVv#~5xd\s,[~w]-J!)|%=]> =?utf-8?q?+=0A=09=7EohchhkRGW=3F=7C6=5FqTmkd=5Ft=3FLZC=23Q-=60=2E=60Y=2Ea=5E?= =?utf-8?q?3zb?=) =?utf-8?q?+U-JVN=5DWT=25cw=23=5BYo0=267C=26bL12wWGlZi=0A=09=7EJ=3B=5Cwg?= =?utf-8?q?=3B3zRnz?=,J"CT_)=\H'1/{?SR7GDu?WIopm.HaBG=QYj"NZD_[zrM\Gip^U MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200909161722.37606.arnd@arndb.de> X-Provags-ID: V01U2FsdGVkX183NgoHRjP+YMpSUMaf5FtblG94v60hZ/3Ypkh Ri9RT/XitRuOjEQbTeZxkBV/8TLJog+qnlu0nAzln0gSJI10zS da66O/5qGbUhklrhq8r3A== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1257 Lines: 26 On Wednesday 16 September 2009, Michael S. Tsirkin wrote: > On Wed, Sep 16, 2009 at 04:57:42PM +0200, Arnd Bergmann wrote: > > On Tuesday 15 September 2009, Michael S. Tsirkin wrote: > > > Userspace in x86 maps a PCI region, uses it for communication with ppc? > > > > This might have portability issues. On x86 it should work, but if the > > host is powerpc or similar, you cannot reliably access PCI I/O memory > > through copy_tofrom_user but have to use memcpy_toio/fromio or readl/writel > > calls, which don't work on user pointers. > > > > Specifically on powerpc, copy_from_user cannot access unaligned buffers > > if they are on an I/O mapping. > > > We are talking about doing this in userspace, not in kernel. Ok, that's fine then. I thought the idea was to use the vhost_net driver to access the user memory, which would be a really cute hack otherwise, as you'd only need to provide the eventfds from a hardware specific driver and could use the regular virtio_net on the other side. Arnd <>< -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/