Joerg Roedel wrote: > On Thu, Jul 01, 2010 at 03:00:17PM -0700, Zach Pfeffer wrote: >> Additionally, the current IOMMU interface does not allow users to >> associate one page table with multiple IOMMUs [...] > > Thats not true. Multiple IOMMUs are completly handled by the IOMMU > drivers. In the case of the IOMMU-API backend drivers this also includes > the ability to use page-tables on multiple IOMMUs. Yeah. I see that now. > >> Since the particular topology is run-time configurable all of these >> use-cases and more can be expressed without pushing the topology into >> the low-level IOMMU driver. > > The IOMMU driver has to know about the topology anyway because it needs > to know which IOMMU it needs to program for a particular device. Perhaps, but why not create a VCM which can be shared across all mappers in the system? Why bury it in a device driver and make all IOMMU device drivers managed their own virtual spaces? Practically this would entail a minor refactor to the fledging IOMMU interface; adding associate and activate ops. > >> Already, there are ~20 different IOMMU map implementations in the >> kernel. Had the Linux kernel had the VCMM, many of those >> implementations could have leveraged the mapping and topology >> management of a VCMM, while focusing on a few key hardware specific >> functions (map this physical address, program the page table base >> register). > > I partially agree here. All the IOMMU implementations in the Linux > kernel have a lot of functionality in common where code could be > shared. Work to share code has been done in the past by Fujita Tomonori > but there are more places to work on. I am just not sure if a new > front-end API is the right way to do this. I don't really think its a new front end API. Its just an API that allows easier mapping manipulation than the current APIs. -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>