From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCHv5 3/3] vhost_net: a kernel-level virtio server Date: Wed, 16 Sep 2009 18:13:29 +0300 Message-ID: <20090916151329.GC5513@redhat.com> References: <20090914164750.GB3745@redhat.com> <4AAFFC8E.9010404@gmail.com> <20090915212545.GC27954@redhat.com> <200909161657.42628.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii 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 To: Arnd Bergmann Return-path: Content-Disposition: inline In-Reply-To: <200909161657.42628.arnd@arndb.de> Sender: owner-linux-mm@kvack.org List-Id: netdev.vger.kernel.org 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. > > Arnd <>< We are talking about doing this in userspace, not in kernel. -- MST -- 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