From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753470AbdAHQ1K (ORCPT ); Sun, 8 Jan 2017 11:27:10 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58428 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752816AbdAHQ1C (ORCPT ); Sun, 8 Jan 2017 11:27:02 -0500 Subject: Re: [PATCH v6 07/18] iommu: Implement reserved_regions iommu-group sysfs file To: Joerg Roedel References: <1483643086-2883-1-git-send-email-eric.auger@redhat.com> <1483643086-2883-8-git-send-email-eric.auger@redhat.com> <20170106110039.GL17255@8bytes.org> <888d3750-817c-77d1-8154-e77cf8c3ad4b@redhat.com> <20170106124816.GQ17255@8bytes.org> <0858b719-2888-0645-66d2-56fe698f4e2f@redhat.com> Cc: eric.auger.pro@gmail.com, christoffer.dall@linaro.org, marc.zyngier@arm.com, robin.murphy@arm.com, alex.williamson@redhat.com, will.deacon@arm.com, tglx@linutronix.de, jason@lakedaemon.net, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, drjones@redhat.com, linux-kernel@vger.kernel.org, pranav.sawargaonkar@gmail.com, iommu@lists.linux-foundation.org, punit.agrawal@arm.com, diana.craciun@nxp.com, gpkulkarni@gmail.com, shankerd@codeaurora.org, bharat.bhushan@nxp.com, geethasowjanya.akula@gmail.com From: Auger Eric Message-ID: <24abe958-6a79-5766-653b-b355a85f2be4@redhat.com> Date: Sun, 8 Jan 2017 17:26:53 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <0858b719-2888-0645-66d2-56fe698f4e2f@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Sun, 08 Jan 2017 16:27:02 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 06/01/2017 18:18, Auger Eric wrote: > Hi Joerg, Robin, > > On 06/01/2017 13:48, Joerg Roedel wrote: >> On Fri, Jan 06, 2017 at 12:46:05PM +0100, Auger Eric wrote: >>> On 06/01/2017 12:00, Joerg Roedel wrote: >> >>>> I think it also makes sense to report the type of the reserved region. >>> >>> What is the best practice in that case? Shall we put the type enum >>> values as strings such as: >>> - direct >>> - nomap >>> - msi >>> >>> and document that in Documentation/ABI/testing/sysfs-kernel-iommu_groups >> >> Yes, a string would be good. An probably 'reserved' is a better name >> than nomap? > the iommu_insert_resv_region() function that builds the group reserved > region list sorts all regions and handles the case where there is an > overlap between regions. Current code does not care about the type of > regions. So in case a NOMAP region overlaps with a direct-mapped region, > what is reported to the user space is the superset and the type depends > on the overlap. This was suggested by Robin at some point to handle > overlaps. > > I guess I should merge regions only in case the types equal? > > I remember that Alex thought that user-space should not care so much > about the type of the regions so I tought it was better for the > user-space to have a minimal view of the regions. > > On the other hand, this issue of merging regions of different types > should not happen often but I prefer to highlight the potential issue. > > What is your guidance? Please forget the question. From an API point of view It does not make sense that iommu_insert_resv_region() merges regions of a different types since the type field becomes unreliable. I will fix this. Thanks Eric > > Thanks > > Eric >> >> >> Joerg >>