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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 0A7C5C433DF for ; Mon, 6 Jul 2020 20:45:38 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A460720663 for ; Mon, 6 Jul 2020 20:45:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A460720663 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 6A4C988CC9; Mon, 6 Jul 2020 20:45:37 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id lfA503B0gfS7; Mon, 6 Jul 2020 20:45:35 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id B83FF88C56; Mon, 6 Jul 2020 20:45:35 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id A4677C0891; Mon, 6 Jul 2020 20:45:35 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 173C1C016F for ; Mon, 6 Jul 2020 20:45:35 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 0661787700 for ; Mon, 6 Jul 2020 20:45:35 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ayQ-TyOw2f0y for ; Mon, 6 Jul 2020 20:45:34 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by fraxinus.osuosl.org (Postfix) with ESMTPS id D174C876FF for ; Mon, 6 Jul 2020 20:45:33 +0000 (UTC) IronPort-SDR: TfgHi4aSz/agfUtSHIlD4HG508hdnLP9cX821VGofSQ8v/S2QjbqVFTIo5Hqi9zgjFY7+tHUNt dVxgzsP1i3mg== X-IronPort-AV: E=McAfee;i="6000,8403,9674"; a="232361342" X-IronPort-AV: E=Sophos;i="5.75,321,1589266800"; d="scan'208";a="232361342" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jul 2020 13:45:00 -0700 IronPort-SDR: HQ54mEMKCUzXtq6FROfHo3vaXufoIPMzRPsKg/rpfDrle+IpU136/OqxgQbpjZ8xi9avMS7PNv 5eis0YU1APDg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,321,1589266800"; d="scan'208";a="357565889" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by orsmga001.jf.intel.com with ESMTP; 06 Jul 2020 13:44:59 -0700 Date: Mon, 6 Jul 2020 13:51:37 -0700 From: Jacob Pan To: Jean-Philippe Brucker Subject: Re: IOASID set token Message-ID: <20200706135137.26979271@jacob-builder> In-Reply-To: <20200706103041.GA3214@myrica> References: <20200701232916.38fd7908@jacob-builder> <20200702064825.20f9d2b1@jacob-builder> <20200706103041.GA3214@myrica> Organization: OTC X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Cc: "Tian, Kevin" , "Raj, Ashok" , Jean-Philippe Brucker , "Lu, Baolu" , "iommu@lists.linux-foundation.org" , "Wu, Hao" X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" Hi Jean, Thanks for the feedback, please see replies inline. On Mon, 6 Jul 2020 12:30:41 +0200 Jean-Philippe Brucker wrote: > Hi Jacob, > > On Thu, Jul 02, 2020 at 06:48:25AM -0700, Jacob Pan wrote: > > Hi Jean, > > > > Just realized I should send this to your Linaro account instead of > > ARM. So Hi again :) > > > > On Wed, 1 Jul 2020 23:29:16 -0700 > > Jacob Pan wrote: > > > > > Hi Jean, > > > > > > Have a question for you on whether we can have a fixed token type > > > for ioasid_set. > > > > > > Currently, ioasid_set has an arbitrary token. For VT-d vSVA > > > usage, we choose mm as ioasid_set token to identify PASIDs within > > > a guest. We have multiple in-kernel users of PASIDs such as VFIO, > > > KVM, and VDCM. When an IOASID set is created, there is not a good > > > way to communicate about the token choices. So we have to let > > > VDCM and KVM *assume* mm is used as token, then retrieve > > > ioasid_set based on the token. > > > > > > This assumption of "mm as token" is not a reliable SW > > > architecture. > > I don't see this as a problem. The token type is tied to the IOASID > set, so users that pass those IOASID sets to ioasid_find() can safely > assume that the returned pointer is an mm_struct. That said I'm not > opposed to consolidating the API with explicit types, it could > definitely be more elegant. > In our use case, we need token to ioasid_set lookup. e.g. VFIO creates an ioasid_set with a token. KVM instance needs to know the ioasid_set based on its mm. So ioasid_find() does not know the set until it finds it based on the token and token type. > > > So > > > we are thinking if we can have an explicit ioasid_set token type > > > where mm is used. After all, PASID and mm are closely related. > > > > > > The code change might be the following: > > > 1. add a flag to indicate token type when ioasid_set is allocated, > > > e.g. IOASID_SET_TYPE_MM > > > IOASID_SET_TYPE_ANY > > > 2. other users of the ioasid_set can query if an mm token exists > > > based on the flag IOASID_SET_TYPE_MM, then retrieve the > > > ioasid_set. > > > > > > Existing ioasid_set user can still use arbitrary token under the > > > flag IOASID_SET_TYPE_ANY > > > > > > Would this be an issue for ARM usage? > > In my current implementation of auxiliary domains for Arm SMMU (which > might never be useful enough to go upstream) I don't even use a token > for the private IOASID set. However I still think we should leave the > option to use a type different than mm_struct as token for some > IOASID sets because device drivers (e.g. AMD kfd) may also want to > dip into the IOASID space and use their own token type. > > For the moment, though, we could actually specialize the IOASID API to > only take an mm_struct as token. That would be fine with VT-d. We can use init_mm for host PASID set, process mm for VM set. > For example the functions exported > by the IOASID lib would be: > > ioasid_t ioasid_alloc_mm(set, min, max, struct mm_struct *mm) what is the set argument used for? In my view, ioasid_set and mm are 1:1 mapped. struct ioasid_set *ioasid_alloc_set(void *token, ioasid_t quota) I was thinking we still have APIs for IOASID set alloc/free since we want to embed ioasid_set info in driver data structures for ownership check. > struct mm_struct *ioasid_find_mm(set, ioasid) I don't get why we need ioasid to find the set token. If we put mm_struct* inside ioasid_set, then we can get the token from the set directly. > ... > > And ioasid_alloc(), ioasid_find(), etc would be internal to ioasid.c > and deal with IOASID_SET_TYPE_MM (or even be removed entirely for > now). New users that need different token types could then introduce > their own IOASID_SET_TYPE_* and use the lower-level functions. > I will keep that in mind in my next set. I think it would be much easier to explain with code. My takeaway is that we have a high-level agreement to have explicit mm as token in IOASID APIs. I think we can work out the details with patches. Jacob > Thanks, > Jean [Jacob Pan] _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu