From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33885) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Whx0J-00013X-Ue for qemu-devel@nongnu.org; Wed, 07 May 2014 04:15:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Whx08-0006UU-2m for qemu-devel@nongnu.org; Wed, 07 May 2014 04:15:03 -0400 Received: from e06smtp13.uk.ibm.com ([195.75.94.109]:34589) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Whx07-0006Ti-PW for qemu-devel@nongnu.org; Wed, 07 May 2014 04:14:51 -0400 Received: from /spool/local by e06smtp13.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 7 May 2014 09:14:49 +0100 Date: Wed, 7 May 2014 10:14:43 +0200 From: Greg Kurz Message-ID: <20140507101443.146fc26d@bahia.local> In-Reply-To: References: <20140505074816.25523.71374.stgit@bahia.local> <20140505080520.25523.44406.stgit@bahia.local> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3 3/4] target-ppc: ppc can be either endian List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: QEMU Developers , bharata@linux.vnet.ibm.com, "qemu-ppc@nongnu.org" , Andreas =?UTF-8?B?RsOkcmJlcg==?= , Alexander Graf On Tue, 6 May 2014 19:37:22 +0100 Peter Maydell wrote: > On 5 May 2014 09:07, Greg Kurz wrote: > > POWER7, POWER7+ and POWER8 families use the ILE bit of the LPCR > > special purpose register to decide the endianness to use when > > entering interrupt handlers. When running a Linux guest, this > > provides a hint on the endianness used by the kernel. From a > > QEMU point of view, the information is needed for legacy virtio > > support and crash dump support as well. > > Do you care about the case of: > * kernel bigendian Yes. FWIW, ppc64 is still widely used in big endian mode we don't want to break. > * userspace littleendian (or vice-versa) We don't care about userspace here. We assume that virtio structures are owned by the guest kernel. > * guest kernel passes virtio device through to guest userspace Not sure to understand... could you please point me to an example ? > * guest userspace is doing the manipulation of the device > Hmm... you mean we would have virtio drivers implemented in the guest userspace ? Does that exist ? Please elaborate. > ? > > (Will Deacon just suggested this as a possibility on the > kvm-arm mailing list...) > Just discovered some virtio endian threads in the kvm-arm@ archives... I'll take some time to read. > Also, are we documenting what the process should be for a > virtio implementation to decide the endianness for a particular > architecture? I assume we'd like kvmtool and QEMU to do > the same thing rather than subtly different things... > Sure ! > thanks > -- PMM > Thanks. -- Gregory Kurz kurzgreg@fr.ibm.com gkurz@linux.vnet.ibm.com Software Engineer @ IBM/Meiosys http://www.ibm.com Tel +33 (0)562 165 496 "Anarchy is about taking complete responsibility for yourself." Alan Moore.