From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46436) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cGFvh-0008FZ-1w for qemu-devel@nongnu.org; Sun, 11 Dec 2016 21:01:25 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cGFve-0003Vf-14 for qemu-devel@nongnu.org; Sun, 11 Dec 2016 21:01:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55056) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cGFvd-0003VF-Rk for qemu-devel@nongnu.org; Sun, 11 Dec 2016 21:01:21 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8D0D33B717 for ; Mon, 12 Dec 2016 02:01:20 +0000 (UTC) Date: Mon, 12 Dec 2016 10:01:15 +0800 From: Peter Xu Message-ID: <20161212015602.GJ28693@pxdev.xzpeter.org> References: <1481089965-3888-1-git-send-email-peterx@redhat.com> <1481089965-3888-3-git-send-email-peterx@redhat.com> <20161211051011-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20161211051011-mutt-send-email-mst@kernel.org> Subject: Re: [Qemu-devel] [PATCH for-2.9 2/2] intel_iommu: extend supported guest aw to 48 bits List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: qemu-devel@nongnu.org, jasowang@redhat.com, famz@redhat.com On Sun, Dec 11, 2016 at 05:13:45AM +0200, Michael S. Tsirkin wrote: > On Wed, Dec 07, 2016 at 01:52:45PM +0800, Peter Xu wrote: > > Previously vt-d codes only supports 39 bits iova address width. It won't > > be hard to extend it to 48 bits. > > > > After enabling this, we should be able to map larger iova addresses. > > > > To check whether 48 bits aw is enabled, we can grep in the guest dmesg > > with line: "dmar: Host address width 48" (previously it was 39). > > > > Signed-off-by: Peter Xu > > I suspect we can't do this for old machine types. > Need to behave in compatible ways. Sure. I can do that. Btw, is vt-d iommu still in experimental stage? I am just thinking whether it'll be overkill we add lots of tunables before we have one stable and mature vt-d emulation. > Also, is 48 always enough? 5 level with 57 bits > is just around the corner. Please refer to the discussion with Jason - looks like vt-d spec currently supports only 39/48 bits address width? Please correct if I made a mistake. > And is it always supported? for things like vfio > to work, don't we need to check what does host support? Hmm, yes, we should do that. But until now, we still don't have a complete vfio support. IMHO we can postpone this issue until vfio is fully supported. Thanks, -- peterx