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:liub...@huawei.com] >>> Sent: Thursday, October 12, 2017 5:39 PM >>> To: Jean-Philippe Brucker <jean-philippe.bruc...@arm.com>; Joerg Roedel >>> <j...@8bytes.org>; Liu, Yi L <yi.l....@intel.com> >>> Cc: Lan, Tianyu <tianyu....@intel.com>; Liu, Yi L >>> <yi.l....@linux.intel.com>; Greg >>> Kroah-Hartman <gre...@linuxfoundation.org>; Wysocki, Rafael J >>> <rafael.j.wyso...@intel.com>; LKML <linux-ker...@vger.kernel.org>; >>> iommu@lists.linux-foundation.org; David Woodhouse <dw...@infradead.org> >>> 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. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
