From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35306) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V1OE9-0000XO-CO for qemu-devel@nongnu.org; Mon, 22 Jul 2013 18:05:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V1OE6-0004vw-O2 for qemu-devel@nongnu.org; Mon, 22 Jul 2013 18:05:09 -0400 Received: from mail-oa0-f50.google.com ([209.85.219.50]:48299) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V1OE6-0004vO-J7 for qemu-devel@nongnu.org; Mon, 22 Jul 2013 18:05:06 -0400 Received: by mail-oa0-f50.google.com with SMTP id k7so9681014oag.23 for ; Mon, 22 Jul 2013 15:05:06 -0700 (PDT) From: Anthony Liguori In-Reply-To: References: <1374515411-43818-1-git-send-email-agraf@suse.de> <87vc42jsgf.fsf@codemonkey.ws> <8761w2xti6.fsf@codemonkey.ws> Date: Mon, 22 Jul 2013 17:05:04 -0500 Message-ID: <87siz6qmi7.fsf@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [Qemu-devel] [PATCH 0/9] Add platform bus List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: "qemu-ppc@nongnu.org list:PowerPC" , Alexander Graf , qemu-devel Developers Peter Maydell writes: > On 22 July 2013 20:52, Anthony Liguori wrote: >> Alexander Graf writes: >>> On 22.07.2013, at 21:38, Anthony Liguori wrote: >>> >>> This could be used just the same for ARM's mach-virt, so I'd rather >>> not make it e500 specific. >> >> If someone designed a "virt" machine and didn't include PCI or some >> other sane existing bus... > > "mach-virt" just means "completely described by device tree > with no knowledge hardcoded in the kernel about the platform". Fair enough. > We don't currently have any PCI host controller which is: > (a) for ARM In QEMU? You can make one super easily by just extending PCIHostState. It's just a matter of mapping the index and data registers somewhere. I can't believe it's that hard to get this working in Linux either. > (b) entirely device tree driven I'm not sure what this means, but presumably it wouldn't be hard to do the above. > (c) supported by QEMU This part is easy enough. > (d) with a decent Linux driver See above. > > So mach-virt doesn't have PCI; it will use virtio-mmio, > same as kvmtool for ARM does. That's all well and fine but there are a lot of advantages to having PCI and being able to use all of the features associated with it. It's always tempting to reinvent the wheel when given the chance but I think in the long term, you'll regret it. Regards, Anthony Liguori > > -- PMM