Hi Drew, Ben, and Qinxin, On 8/6/26 4:42 PM, Ben Horgan wrote: > Hi Drew, > > On 06/08/2026 06:23, Drew Fustini wrote: >> On Tue, Jul 14, 2026 at 09:06:50PM +0800, Zhanpeng Zhang wrote: >>> This RFC extends RISC-V CBQRI/resctrl support to external requesters >>> behind a RISC-V IOMMU. >> [..] >>> Open questions for this RFC: >>> >>> * whether a common resctrl "devices" file is the right ABI for >>> associating external requesters with a resource group; >> >> I think a separate file is the right approach to avoid confusing iommu >> groups with pids. >> >> I should note that James Morse had an ARM MPAM "extras" tree [1] which >> carried an iommu_group assignment interface, using the same >> iommu_group:<id> format, but writing it to the tasks file. However, Ben >> Horgan clarified back in March [2] in a reply to Qinxin Xia that it is >> no longer maintained. Ben also wrote that the interface would likely >> change upstream. I've added Ben Horgan and Qinxin Xia to the CC list so >> hopefully they can chime in. > > I haven't thought about the interface much but Reinette let me know here [1], > with good reasons, > that we should consider the format of the tasks file fixed. > > Thanks, > > Ben > > [1] > https://lore.kernel.org/all/[email protected]/ >
Thanks for the useful links and context. I referred to the earlier Arm MPAM IOMMU group assignment work in my test version as well. Given that the tasks ABI should remain PID-only, a separate file for IOMMU group assignment seems to be the reasonable direction. >> >> I plan to review the patches in this series further but I didn't want to >> delay any further in pointing out the above. >> >> Thanks, >> Drew >> >> [1] >> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/log/?h=mpam/snapshot%2Bextras/v6.18-rc1 >> [2] >> https://lore.kernel.org/lkml/[email protected]/ > Thanks, Zhanpeng
