From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean-Philippe Brucker Subject: Re: [PATCH v2 03/40] iommu/sva: Manage process address spaces Date: Thu, 17 May 2018 11:02:42 +0100 Message-ID: References: <20180511190641.23008-1-jean-philippe.brucker@arm.com> <20180511190641.23008-4-jean-philippe.brucker@arm.com> <20180516163117.622693ea@jacob-builder> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180516163117.622693ea@jacob-builder> Content-Language: en-US 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: Jacob Pan Cc: "kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "xuzaibo-hv44wF8Li93QT0dZR+AlfA@public.gmane.org" , Will Deacon , "okaya-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org" , "linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org" , "ashok.raj-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org" , "bharatku-gjFFaj9aHVfQT0dZR+AlfA@public.gmane.org" , "linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "rfranz-YGCgFSpz5w/QT0dZR+AlfA@public.gmane.org" , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "rgummal-gjFFaj9aHVfQT0dZR+AlfA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org" , "ilias.apalodimas-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , "christian.koenig-5C7GfCeVMHo@public.gmane.org" List-Id: devicetree@vger.kernel.org On 17/05/18 00:31, Jacob Pan wrote: > On Fri, 11 May 2018 20:06:04 +0100 > I am a little confused about domain vs. pasid relationship. If > each domain represents a address space, should there be a domain for > each pasid? I don't think there is a formal definition, but from previous discussion the consensus seems to be: domains are a collection of devices that have the same virtual address spaces (one or many). Keeping that definition makes things easier, in my opinion. Some time ago, I did try to represent PASIDs using "subdomains" (introducing a hierarchy of struct iommu_domain), but it required invasive changes in the IOMMU subsystem and probably all over the tree. You do need some kind of "root domain" for each device, so that "iommu_get_domain_for_dev()" still makes sense. That root domain doesn't have a single address space but a collection of subdomains. If you need this anyway, representing a PASID with an iommu_domain doesn't seem preferable than using a different structure (io_mm), because they don't have anything in common. Thanks, Jean