From mboxrd@z Thu Jan 1 00:00:00 1970 From: Auger Eric Subject: Re: [PATCH v6 07/18] iommu: Implement reserved_regions iommu-group sysfs file Date: Sun, 8 Jan 2017 17:26:53 +0100 Message-ID: <24abe958-6a79-5766-653b-b355a85f2be4@redhat.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <0858b719-2888-0645-66d2-56fe698f4e2f-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Joerg Roedel Cc: drjones-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, jason-NLaQJdtUoK4Be96aLqz0jA@public.gmane.org, kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, marc.zyngier-5wv7dgnIgG8@public.gmane.org, punit.agrawal-5wv7dgnIgG8@public.gmane.org, will.deacon-5wv7dgnIgG8@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, geethasowjanya.akula-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, pranav.sawargaonkar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, shankerd-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, gpkulkarni-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, christoffer.dall-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, eric.auger.pro-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org List-Id: iommu@lists.linux-foundation.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 >>