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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 BBEBEC43381 for ; Thu, 28 Feb 2019 18:30:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 98BFC218AE for ; Thu, 28 Feb 2019 18:30:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733281AbfB1Sal (ORCPT ); Thu, 28 Feb 2019 13:30:41 -0500 Received: from mga11.intel.com ([192.55.52.93]:4536 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726093AbfB1Sak (ORCPT ); Thu, 28 Feb 2019 13:30:40 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Feb 2019 10:30:40 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,423,1544515200"; d="scan'208";a="142457349" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by orsmga001.jf.intel.com with ESMTP; 28 Feb 2019 10:30:39 -0800 Date: Thu, 28 Feb 2019 10:32:52 -0800 From: Jacob Pan To: Jean-Philippe Brucker Cc: Joerg Roedel , "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , "christian.koenig@amd.com" , "kevin.tian@intel.com" , "ashok.raj@intel.com" , "baolu.lu@linux.intel.com" , "alex.williamson@redhat.com" , jacob.jun.pan@linux.intel.com Subject: Re: [PATCH 1/1] iommu: Bind process address spaces to devices Message-ID: <20190228103252.69715c67@jacob-builder> In-Reply-To: References: <20190220142759.33308-1-jean-philippe.brucker@arm.com> <20190220142759.33308-2-jean-philippe.brucker@arm.com> <20190226111743.GK20740@8bytes.org> <20190227134129.51ad42ac@jacob-builder> Organization: OTC X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 28 Feb 2019 12:19:22 +0000 Jean-Philippe Brucker wrote: > On 27/02/2019 21:41, Jacob Pan wrote: > > On Tue, 26 Feb 2019 12:17:43 +0100 > > Joerg Roedel wrote: > > > >> Hi Jean-Philippe, > >> > >> Thanks for the patch! I think this is getting close to be applied > >> after the next merge window. > >> > >> On Wed, Feb 20, 2019 at 02:27:59PM +0000, Jean-Philippe Brucker > >> wrote: > >>> +int iommu_sva_bind_device(struct device *dev, struct mm_struct > >>> *mm, int *pasid, > >>> + iommu_mm_exit_handler_t mm_exit, void > >>> *drvdata) > >> > >> I think we are better of with introducing a sva-bind handle which > >> can be used to extend and further configure the binding done with > >> this function. > >> > >> How about a 'struct iommu_sva' with an iommu-private definition > >> that is returned by this function: > >> > >> struct iommu_sva *iommu_sva_bind_device(struct device *dev, > >> struct mm_struct > >> *mm); > > Just trying to understand how to use this API. > > So if we bind the same mm to two different devices, we should get > > two different iommu_sva handle, right? > > Yes, the iommu_sva handle is the bond between one mm and one device, > so you will get two different handles. > > > I think intel-svm still needs a flag argument for supervisor pasid > > etc. Other than that, I think both interface should work for vt-d. > > Is supervisor PASID still needed now that we have auxiliary domains, > and now that VT-d supports nested IOVA? You could have private kernel > address spaces through auxiliary domains, or simply use DMA API as > usual with PASID#0. I've been reluctant to make that feature common > because it looks risky - gives full access to the kernel address > space to devices and no notification on mapping change. > It is still in the VT-d spec. Ashok will be able to answer this better :) > > Another question is that for nested SVA, we will need to bind guest > > mm. Do you think we should try to reuse this or have it separate? I > > am working on a separate API for now. > > I also think it should be separate. That bind() operation is performed > on an auxiliary domain, I guess? > yes the 2nd level is retrieved from aux domain for mdev, but for pdev, 2nd level comes from rid2pasid/default domain. > >> and the corresponding unbind function: > >> > >> int iommu_sva_unbind_device(struct iommu_sva* *handle); > >> > >> (Btw, does this need to return and int? Can unbinding fail?). > >> > >> With that in place we can implement and extentable API base on the > >> handle: > >> > >> int iommu_sva_get_pasid(struct iommu_sva *handle); > > If multiple bind to the same mm gets multiple handles, this API > > should retrieve the same pasid for different handle? > > Yes > > > Just curious why making > > the handle private instead of returning the pasid value in the > > handle? > > I don't have a strong objection against that. One reason to have an > accessor is that the PASID is freed on mm_exit, so until the device > driver calls unbind(), the PASID contained in the handle is stale (and > the accessor returns PASID_INVALID). But that's a bit pedantic, the > device driver should know that the handle is stale since it got > notified of it. Having an accessor might also help tracking uses of > the handle in the kernel, and make future API modifications easier. > make sense. > Thanks, > Jean > > >> void iommu_sva_set_exit_handler(struct iommu_sva *handle, > >> iommu_mm_exit_handler_t > >> mm_exit); > >> > >> I think at least the AMD IOMMU driver needs more call-backs like a > >> handler that is invoked when a fault can not be resolved. And there > >> might be others in the future, putting them all in the parameter > >> list of the bind function doesn't scale well. > >> > > > >> Regards, > >> > >> Joerg > > > > > [Jacob Pan]