From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752767AbdJLKVy (ORCPT ); Thu, 12 Oct 2017 06:21:54 -0400 Received: from foss.arm.com ([217.140.101.70]:43156 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752114AbdJLKVx (ORCPT ); Thu, 12 Oct 2017 06:21:53 -0400 Subject: Re: [PATCH v2 03/16] iommu: introduce iommu invalidate API function To: Bob Liu , "Liu, Yi L" , Joerg Roedel Cc: "Lan, Tianyu" , "Liu, Yi L" , Greg Kroah-Hartman , "Wysocki, Rafael J" , LKML , "iommu@lists.linux-foundation.org" , David Woodhouse References: <1507244624-39189-1-git-send-email-jacob.jun.pan@linux.intel.com> <1507244624-39189-4-git-send-email-jacob.jun.pan@linux.intel.com> <20171010133542.juag7cwbivlb56sl@8bytes.org> <20171010150953.4095a045@jacob-builder> <20171011095126.GD30803@8bytes.org> <20171011121534.GG30803@8bytes.org> <3cdbce19-9264-b2d0-745b-8d32d5b8cfe7@arm.com> <541498d5-0478-0b9a-6c01-12f7dc30ebf3@huawei.com> <5cc5b52c-27da-7bb5-4968-e46ed6d44fc0@huawei.com> From: Jean-Philippe Brucker Message-ID: Date: Thu, 12 Oct 2017 11:26:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <5cc5b52c-27da-7bb5-4968-e46ed6d44fc0@huawei.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/10/17 11:07, Bob Liu wrote: > On 2017/10/12 17:50, Liu, Yi L wrote: >> >> >>> -----Original Message----- >>> From: Bob Liu [mailto:liubo95@huawei.com] >>> Sent: Thursday, October 12, 2017 5:39 PM >>> To: Jean-Philippe Brucker ; Joerg Roedel >>> ; Liu, Yi L >>> Cc: Lan, Tianyu ; Liu, Yi L ; Greg >>> Kroah-Hartman ; Wysocki, Rafael J >>> ; LKML ; >>> iommu@lists.linux-foundation.org; David Woodhouse >>> Subject: Re: [PATCH v2 03/16] iommu: introduce iommu invalidate API function >>> >>> On 2017/10/11 20:48, Jean-Philippe Brucker wrote: >>>> On 11/10/17 13:15, Joerg Roedel wrote: >>>>> On Wed, Oct 11, 2017 at 11:54:52AM +0000, Liu, Yi L wrote: >>>>>> I didn't quite get 'iovm' mean. Can you explain a bit about the idea? >>>>> >>>>> It's short for IO Virtual Memory, basically a replacement term for 'svm' >>>>> that is not ambiguous (afaik) and not specific to Intel. >>>> >>>> I wonder if SVM originated in OpenCL first, rather than intel? That's >>>> why I'm using it, but it is ambiguous. I'm not sure IOVM is precise >>>> enough though, since the name could as well be used without shared >>>> tables, for classical map/unmap and IOVAs. Kevin Tian suggested SVA >>>> "Shared Virtual Addressing" last time, which is a little more clear >>>> than SVM and isn't used elsewhere in the kernel either. >>>> >>> >>> The process "vaddr" can be the same as "IOVA" by using the classical map/unmap >>> way. >>> This is also a kind of share virtual memory/address(except have to pin physical >>> memory). >>> How to distinguish these two different implementation of "share virtual >>> memory/address"? >>> >> [Liu, Yi L] Not sure if I get your idea well. Process "vaddr" is owned by process and >> maintained by mmu, while "IOVA" is maintained by iommu. So they are different in the >> way they are maintained. Since process "vaddr" is maintained by mmu and then used by >> iommu, so we call it shared virtual memory/address. This is how "shared" term comes. > > I think from the view of application, the share virtual memory/address(or Nvidia-CUDA unify virtual address) is like this: > > 1. vaddr = malloc(); e.g vaddr=0x10000 > 2. device can get the same data(accessing the same physical memory) through same address e.g 0x10000, and don't care about it's a vaddr or IOVA.. > (actually in Nvidia-cuda case, the data will be migrated between system-ddr and gpu-memory, but the vaddr is always the same for CPU and GPU). > > So there are two ways(beside Nvidia way) to implement this requirement: > 1) > get the physical memory of vaddr; > dma_map the paddr to iova; > If we appoint iova = vaddr (e.g iova can be controlled by the user space driver through vfio DMA_MAP), > This can also be called share virtual address between CPU process and device.. This could probably be implemented by augmenting the iommu_map/unmap API to take a PASID, as the mm subsystem isn't really involved and there isn't any need for bind/unbind. Maybe we should continue the conversation on the other thread though, since this one is about sharing PASID tables with a guest. Thanks, Jean > 2) > The second way is what this RFC did.