On Wed, Jun 19, 2024, Fuad Tabba wrote: > Hi Jason, > > On Wed, Jun 19, 2024 at 12:51 PM Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > > > > On Wed, Jun 19, 2024 at 10:11:35AM +0100, Fuad Tabba wrote: > > > > > To be honest, personally (speaking only for myself, not necessarily > > > for Elliot and not for anyone else in the pKVM team), I still would > > > prefer to use guest_memfd(). I think that having one solution for > > > confidential computing that rules them all would be best. But we do > > > need to be able to share memory in place, have a plan for supporting > > > huge pages in the near future, and migration in the not-too-distant > > > future. > > > > I think using a FD to control this special lifetime stuff is > > dramatically better than trying to force the MM to do it with struct > > page hacks. > > > > If you can't agree with the guest_memfd people on how to get there > > then maybe you need a guest_memfd2 for this slightly different special > > stuff instead of intruding on the core mm so much. (though that would > > be sad) > > > > We really need to be thinking more about containing these special > > things and not just sprinkling them everywhere. > > I agree that we need to agree :) This discussion has been going on > since before LPC last year, and the consensus from the guest_memfd() > folks (if I understood it correctly) is that guest_memfd() is what it > is: designed for a specific type of confidential computing, in the > style of TDX and CCA perhaps, and that it cannot (or will not) perform > the role of being a general solution for all confidential computing. That isn't remotely accurate. I have stated multiple times that I want guest_memfd to be a vehicle for all VM types, i.e. not just CoCo VMs, and most definitely not just TDX/SNP/CCA VMs. What I am staunchly against is piling features onto guest_memfd that will cause it to eventually become virtually indistinguishable from any other file-based backing store. I.e. while I want to make guest_memfd usable for all VM *types*, making guest_memfd the preferred backing store for all *VMs* and use cases is very much a non-goal.
