On Wed, Apr 17, 2024 at 08:01:10AM +0000, Shameerali Kolothum Thodi wrote: > We do have plans to revive the SMMUv3 ECMDQ series posted a while back[0] > and looking at this series, I am just wondering whether it makes sense to have > a similar one with ECMDQ as well? I see that the NVIDIA VCMDQ has a special bit > to restrict the commands that can be issued from user space. If we end up assigning > a ECMDQ to user space, is there any potential risk in doing so? I think there is some risk/trouble, ECMDQ needs some enhancement before it can be really safe to use from less privileged software, and it wasn't designed to have an isolated doorbell page either. > Not clear to me what are the major concerns here and maybe we can come up with > something to address that in kernel. I haven't looked deeply but my impression has been the ECMDQ is not workable to support virtualization. At a minimum it has no way to constrain the command flow to a VMID and to do VSID -> PSID translation. I suggest you talk directly to ARM on this if you are interested in this. Jason
