> From: Jason Gunthorpe <jgg@xxxxxxxxxx> > Sent: Friday, December 17, 2021 4:49 AM > > On Sat, Dec 11, 2021 at 03:57:45AM +0000, Tian, Kevin wrote: > > > This might be the only open as I still didn't see why we need an > > explicit flag to claim a 'full device' thing. From kernel p.o.v the > > ARM case is no different from Intel that both allows an user > > page table attached to vRID, just with different format and > > addr width (Intel is 64bit, ARM is 84bit where PASID can be > > considered a sub-handle in the 84bit address space and not > > the kernel's business). > > I think the difference is intention. > > In one case the kernel is saying 'attach a RID and I intend to use > PASID' in which case the kernel user can call the PASID APIs. > > The second case is saying 'I will not use PASID'. > > They are different things and I think it is a surprising API if the > kernel user attaches a domain, intends to use PASID and then finds out > it can't, eg because an ARM user page table was hooked up. > > If you imagine the flag as 'I intend to use PASID' I think it makes a > fair amount of sense from an API design too. > > We could probably do without it, at least for VFIO and qemu cases, but > it seems a little bit peculiar to me. > ok, combining the kernel user makes the flag more sensible. Thanks Kevin
