From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5FC83C433C1 for ; Thu, 25 Mar 2021 18:22:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19028619FB for ; Thu, 25 Mar 2021 18:22:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230042AbhCYSVo (ORCPT ); Thu, 25 Mar 2021 14:21:44 -0400 Received: from mga03.intel.com ([134.134.136.65]:31048 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230046AbhCYSVR (ORCPT ); Thu, 25 Mar 2021 14:21:17 -0400 IronPort-SDR: DZV6YdxdedK4GmDONw5Mcub2ssAJhiST5sSIQePk5F1nDpAFJmFOEMGf8I82LrKvY/ejVYHnGy bCMZuwcwd2+A== X-IronPort-AV: E=McAfee;i="6000,8403,9934"; a="191026142" X-IronPort-AV: E=Sophos;i="5.81,278,1610438400"; d="scan'208";a="191026142" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2021 11:21:00 -0700 IronPort-SDR: iNmYQYa5hzPyJPYl+zaoyyX+P7oJAxSYwM0PTYjXWfpcbrZ4bWNOck+Me3PtDnGWcTcNThyAQI SQuXXWnaR79w== X-IronPort-AV: E=Sophos;i="5.81,278,1610438400"; d="scan'208";a="416135927" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2021 11:21:00 -0700 Date: Thu, 25 Mar 2021 11:23:27 -0700 From: Jacob Pan To: Jason Gunthorpe Cc: Jean-Philippe Brucker , LKML , Joerg Roedel , Lu Baolu , David Woodhouse , iommu@lists.linux-foundation.org, cgroups@vger.kernel.org, Tejun Heo , Li Zefan , Johannes Weiner , Jean-Philippe Brucker , Alex Williamson , Eric Auger , Jonathan Corbet , Raj Ashok , "Tian, Kevin" , Yi Liu , Wu Hao , Dave Jiang , jacob.jun.pan@linux.intel.com Subject: Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs Message-ID: <20210325112327.24860e3f@jacob-builder> In-Reply-To: <20210325171645.GF2356281@nvidia.com> References: <20210319124645.GP2356281@nvidia.com> <20210319135432.GT2356281@nvidia.com> <20210319112221.5123b984@jacob-builder> <20210324100246.4e6b8aa1@jacob-builder> <20210324170338.GM2356281@nvidia.com> <20210324151230.466fd47a@jacob-builder> <20210325100236.17241a1c@jacob-builder> <20210325171645.GF2356281@nvidia.com> Organization: OTC X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jason, On Thu, 25 Mar 2021 14:16:45 -0300, Jason Gunthorpe wrote: > On Thu, Mar 25, 2021 at 10:02:36AM -0700, Jacob Pan wrote: > > Hi Jean-Philippe, > > > > On Thu, 25 Mar 2021 11:21:40 +0100, Jean-Philippe Brucker > > wrote: > > > > > On Wed, Mar 24, 2021 at 03:12:30PM -0700, Jacob Pan wrote: > > > > 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; > > > > } > > > > > > Does that allow PASID allocation during driver probe, in kernel_init > > > or modprobe context? > > > > > Good point. Yes, you can get cgroup subsystem state in kernel_init for > > charging/uncharging. I would think module_init should work also since > > it is after kernel_init. I have tried the following: > > static int __ref kernel_init(void *unused) > > { > > int ret; > > + struct cgroup_subsys_state *css; > > + css = task_get_css(current, pids_cgrp_id); > > > > But that would imply: > > 1. IOASID has to be built-in, not as module > > 2. IOASIDs charged on PID1/init would not subject to cgroup limit since > > it will be in the root cgroup and we don't support migration nor will > > migrate. > > > > Then it comes back to the question of why do we try to limit in-kernel > > users per cgroup if we can't enforce these cases. > > Are these real use cases? Why would a driver binding to a device > create a single kernel pasid at bind time? Why wouldn't it use > untagged DMA? > For VT-d, I don't see such use cases. All PASID allocations by the kernel drivers has proper process context. > When someone needs it they can rework it and explain why they are > doing something sane. > Agreed. > Jason Thanks, Jacob