> -----Original Message----- > From: Jason Gunthorpe <jgg@xxxxxxxxxx> > Sent: Wednesday, April 17, 2024 1:25 PM > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> > Cc: Nicolin Chen <nicolinc@xxxxxxxxxx>; will@xxxxxxxxxx; > robin.murphy@xxxxxxx; joro@xxxxxxxxxx; thierry.reding@xxxxxxxxx; > vdumpa@xxxxxxxxxx; jonathanh@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > iommu@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux- > tegra@xxxxxxxxxxxxxxx; Jerry Snitselaar <jsnitsel@xxxxxxxxxx> > Subject: Re: [PATCH v5 0/6] Add Tegra241 (Grace) CMDQV Support (part 1/2) > > 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. Ok. That makes sense. > > I suggest you talk directly to ARM on this if you are interested in > this. > Sure. Will check. Thanks, Shameer
