From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759546Ab3BYAN1 (ORCPT ); Sun, 24 Feb 2013 19:13:27 -0500 Received: from ozlabs.org ([203.10.76.45]:41429 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758404Ab3BYAN0 (ORCPT ); Sun, 24 Feb 2013 19:13:26 -0500 Date: Mon, 25 Feb 2013 11:03:22 +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: <20130225000322.GN30946@truffula.fritz.box> References: <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> <20130222000415.GI21011@truffula.fritz.box> <1361506273.2801.327.camel@bling.home> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="F7w+4yMapWozG0Ib" Content-Disposition: inline In-Reply-To: <1361506273.2801.327.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 --F7w+4yMapWozG0Ib Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Feb 21, 2013 at 09:11:13PM -0700, Alex Williamson wrote: > On Fri, 2013-02-22 at 11:04 +1100, David Gibson wrote: > > 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 coup= le > > > > > 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 ju= st > > > > 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 t= han > > > code to parse directory entries and the future maintenance of an > > > unrestricted grab bag of sysfs entries? > >=20 > > 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 > A group is an association of devices based on isolation and visibility. > The dma window happens to be associated with a group on your platform, > but that's not always the case. It's certainly an iommu driver specific group property, but a group property nonetheless. > This is why I was hoping something in > sysfs already reported the dma window so that we could point to it > rather than creating an interface where it doesn't really belong. Alas, no. There's been no reason to expose PEs previously. --=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 --F7w+4yMapWozG0Ib Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlEqqkoACgkQaILKxv3ab8ZERwCfZCL8DaFxn+x9wNLHs84DEfJD QFEAnj7UA8EAxAfDs00nGBzEMj7Ehj9T =4K+c -----END PGP SIGNATURE----- --F7w+4yMapWozG0Ib--