From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754951Ab3BVBWm (ORCPT ); Thu, 21 Feb 2013 20:22:42 -0500 Received: from ozlabs.org ([203.10.76.45]:57165 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753970Ab3BVBWk (ORCPT ); Thu, 21 Feb 2013 20:22:40 -0500 Date: Fri, 22 Feb 2013 11:04:15 +1100 From: David Gibson To: Alex Williamson Cc: Alexey Kardashevskiy , Joerg Roedel , Benjamin Herrenschmidt , linux-kernel@vger.kernel.org Subject: Re: [PATCH] iommu: making IOMMU sysfs nodes API public Message-ID: <20130222000415.GI21011@truffula.fritz.box> References: <1360628713.3248.8.camel@bling.home> <1360642004-7419-1-git-send-email-aik@ozlabs.ru> <1360645643.3248.91.camel@bling.home> <511A54DC.9030908@ozlabs.ru> <1360689304.3248.154.camel@bling.home> <5121C709.80007@ozlabs.ru> <1361251440.2801.142.camel@bling.home> <20130219073853.GS21067@truffula.fritz.box> <1361304711.2801.232.camel@bling.home> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="oxV4ZoPwBLqAyY+a" Content-Disposition: inline In-Reply-To: <1361304711.2801.232.camel@bling.home> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --oxV4ZoPwBLqAyY+a Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Feb 19, 2013 at 01:11:51PM -0700, Alex Williamson wrote: > On Tue, 2013-02-19 at 18:38 +1100, David Gibson wrote: > > On Mon, Feb 18, 2013 at 10:24:00PM -0700, Alex Williamson wrote: > > > On Mon, 2013-02-18 at 17:15 +1100, Alexey Kardashevskiy wrote: [snip] > > > Adding the window size to sysfs seems more readily convenient, > > > but is it so hard for userspace to open the files and call a couple > > > ioctls to get far enough to call IOMMU_GET_INFO? I'm unconvinced the > > > clutter in sysfs more than just a quick fix. Thanks, > >=20 > > And finally, as Alexey points out, isn't the point here so we know how > > much rlimit to give qemu? Using ioctls we'd need a special tool just > > to check the dma window sizes, which seems a bit hideous. >=20 > Is it more hideous that using iommu groups to report a vfio imposed > restriction? Are a couple open files and a handful of ioctls worse than > code to parse directory entries and the future maintenance of an > unrestricted grab bag of sysfs entries? The fact that the memory is locked is a vfio restriction, but the actual dma window size is, genuinely, a property of the group. --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson --oxV4ZoPwBLqAyY+a Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlEmtf8ACgkQaILKxv3ab8Yx2wCeIZi02eSK4V91QamKoq1R4LQb jrAAniA1BHfvqKgrn+e+59edyq2MXpSM =XHeH -----END PGP SIGNATURE----- --oxV4ZoPwBLqAyY+a--