From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43549) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YDBxF-00044E-T4 for qemu-devel@nongnu.org; Mon, 19 Jan 2015 08:01:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YDBxA-00064k-JU for qemu-devel@nongnu.org; Mon, 19 Jan 2015 08:01:17 -0500 Received: from mail-wg0-x22c.google.com ([2a00:1450:400c:c00::22c]:61672) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YDBxA-00064g-CM for qemu-devel@nongnu.org; Mon, 19 Jan 2015 08:01:12 -0500 Received: by mail-wg0-f44.google.com with SMTP id y19so31613508wgg.3 for ; Mon, 19 Jan 2015 05:01:11 -0800 (PST) Sender: Paolo Bonzini Message-ID: <54BD0013.5040201@redhat.com> Date: Mon, 19 Jan 2015 14:01:07 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <20150119134937.6c58c242@bahia.local> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] virtio_tswaps() vs virtio_ld/st_p() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell , Greg Kurz Cc: Stefan Hajnoczi , qemu-devel On 19/01/2015 13:53, Peter Maydell wrote: > > Heh, not sure I would have provided such a comprehensive answer. :) > > ...so now I have a question: what semantics does virtio expect > for its virtio_ld*/st*_phys accessors if QEMU is emulating a > CPU with virtualization support? Is the assumption just that > the guest that's using virtio has a 1:1 mapping of what it > thinks are physical addresses to real guest physical addresses? Right now, the semantics are "PPC uses DMA addresses, everything else uses physical addresses". However, this could be changed since x86 IOMMU support is still experimental, and without an IOMMU DMA addresses _are_ physical addresses. Paolo