Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934978AbcJ0Nxk (ORCPT ); Thu, 27 Oct 2016 09:53:40 -0400 Received: from hqemgate16.nvidia.com ([216.228.121.65]:15744 "EHLO hqemgate16.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936684AbcJ0NwY (ORCPT ); Thu, 27 Oct 2016 09:52:24 -0400 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Wed, 26 Oct 2016 17:32:11 -0700 Subject: Re: [Qemu-devel] [PATCH v9 04/12] vfio iommu: Add support for mediated devices To: Alexey Kardashevskiy , , , , References: <1476739332-4911-1-git-send-email-kwankhede@nvidia.com> <1476739332-4911-5-git-send-email-kwankhede@nvidia.com> CC: , , , , , X-Nvconfidentiality: public From: Kirti Wankhede Message-ID: Date: Thu, 27 Oct 2016 18:01:51 +0530 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.24.70.209] X-ClientProxiedBy: DRUKMAIL102.nvidia.com (10.25.59.20) To bgmail102.nvidia.com (10.25.59.11) Content-Type: text/plain; charset="koi8-r" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2647 Lines: 64 On 10/27/2016 12:50 PM, Alexey Kardashevskiy wrote: > On 18/10/16 08:22, Kirti Wankhede wrote: >> VFIO IOMMU drivers are designed for the devices which are IOMMU capable. >> Mediated device only uses IOMMU APIs, the underlying hardware can be >> managed by an IOMMU domain. >> >> Aim of this change is: >> - To use most of the code of TYPE1 IOMMU driver for mediated devices >> - To support direct assigned device and mediated device in single module >> >> Added two new callback functions to struct vfio_iommu_driver_ops. Backend >> IOMMU module that supports pining and unpinning pages for mdev devices >> should provide these functions. >> Added APIs for pining and unpining pages to VFIO module. These calls back >> into backend iommu module to actually pin and unpin pages. >> >> This change adds pin and unpin support for mediated device to TYPE1 IOMMU >> backend module. More details: >> - When iommu_group of mediated devices is attached, task structure is >> cached which is used later to pin pages and page accounting. > > > For SPAPR TCE IOMMU driver, I ended up caching mm_struct with > atomic_inc(&container->mm->mm_count) (patches are on the way) instead of > using @current or task as the process might be gone while VFIO container is > still alive and @mm might be needed to do proper cleanup; this might not be > an issue with this patchset now but still you seem to only use @mm from > task_struct. > Consider the example of QEMU process which creates VFIO container, QEMU in its teardown path would release the container. How could container be alive when process is gone? Kirti > > >> - It keeps track of pinned pages for mediated domain. This data is used to >> verify unpinning request and to unpin remaining pages while detaching, if >> there are any. >> - Used existing mechanism for page accounting. If iommu capable domain >> exist in the container then all pages are already pinned and accounted. >> Accouting for mdev device is only done if there is no iommu capable >> domain in the container. >> - Page accouting is updated on hot plug and unplug mdev device and pass >> through device. >> >> Tested by assigning below combinations of devices to a single VM: >> - GPU pass through only >> - vGPU device only >> - One GPU pass through and one vGPU device >> - Linux VM hot plug and unplug vGPU device while GPU pass through device >> exist >> - Linux VM hot plug and unplug GPU pass through device while vGPU device >> exist >> >> Signed-off-by: Kirti Wankhede >> Signed-off-by: Neo Jia >> Change-Id: I295d6f0f2e0579b8d9882bfd8fd5a4194b97bd9a > >