From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id 982136B004F for ; Wed, 16 Sep 2009 10:57:46 -0400 (EDT) From: Arnd Bergmann Subject: Re: [PATCHv5 3/3] vhost_net: a kernel-level virtio server Date: Wed, 16 Sep 2009 16:57:42 +0200 References: <20090914164750.GB3745@redhat.com> <4AAFFC8E.9010404@gmail.com> <20090915212545.GC27954@redhat.com> In-Reply-To: <20090915212545.GC27954@redhat.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200909161657.42628.arnd@arndb.de> Sender: owner-linux-mm@kvack.org To: "Michael S. Tsirkin" 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 List-ID: 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. Arnd <>< -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org