From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacob Pan Subject: Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs Date: Wed, 24 Mar 2021 15:12:30 -0700 Message-ID: <20210324151230.466fd47a@jacob-builder> References: <1614463286-97618-1-git-send-email-jacob.jun.pan@linux.intel.com> <1614463286-97618-6-git-send-email-jacob.jun.pan@linux.intel.com> <20210318172234.3e8c34f7@jacob-builder> <20210319124645.GP2356281@nvidia.com> <20210319135432.GT2356281@nvidia.com> <20210319112221.5123b984@jacob-builder> <20210324100246.4e6b8aa1@jacob-builder> <20210324170338.GM2356281@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20210324170338.GM2356281-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Sender: "iommu" To: Jason Gunthorpe Cc: Jean-Philippe Brucker , "Tian, Kevin" , Alex Williamson , Raj Ashok , Jonathan Corbet , Jean-Philippe Brucker , LKML , Dave Jiang , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Li Zefan , Johannes Weiner , Tejun Heo , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Wu Hao , David Woodhouse Hi Jason, On Wed, 24 Mar 2021 14:03:38 -0300, Jason Gunthorpe wrote: > On Wed, Mar 24, 2021 at 10:02:46AM -0700, Jacob Pan wrote: > > > Also wondering about device driver allocating auxiliary domains for > > > their private use, to do iommu_map/unmap on private PASIDs (a clean > > > replacement to super SVA, for example). Would that go through the > > > same path as /dev/ioasid and use the cgroup of current task? > > > > For the in-kernel private use, I don't think we should restrict based on > > cgroup, since there is no affinity to user processes. I also think the > > PASID allocation should just use kernel API instead of /dev/ioasid. Why > > would user space need to know the actual PASID # for device private > > domains? Maybe I missed your idea? > > There is not much in the kernel that isn't triggered by a process, I > would be careful about the idea that there is a class of users that > can consume a cgroup controlled resource without being inside the > cgroup. > > We've got into trouble before overlooking this and with something > greenfield like PASID it would be best built in to the API to prevent > a mistake. eg accepting a cgroup or process input to the allocator. > Make sense. But I think we only allow charging the current cgroup, how about I add the following to ioasid_alloc(): misc_cg = get_current_misc_cg(); ret = misc_cg_try_charge(MISC_CG_RES_IOASID, misc_cg, 1); if (ret) { put_misc_cg(misc_cg); return ret; } BTW, IOASID will be one of the resources under the proposed misc cgroup. Thanks, Jacob