On Fri, Jul 22, 2022, Borislav Petkov wrote: > On Thu, Jun 23, 2022 at 10:43:40PM +0000, Kalra, Ashish wrote: > > Yes, that's a nice way to hide it from the rest of the kernel which > > does not require access to this structure anyway, in essence, it > > becomes a private structure. > > So this whole discussion whether there should be a model check or not > in case a new RMP format gets added in the future is moot - when a new > model format comes along, *then* the distinction should be done and > added in code - not earlier. I disagree. Running an old kernel on new hardware with a different RMP layout should refuse to use SNP, not read/write garbage and likely corrupt the RMP and/or host memory. And IMO, hiding the non-architectural RMP format in SNP-specific code so that we don't have to churn a bunch of call sites that don't _need_ access to the raw RMP format is a good idea regardless of whether we want to be optimistic or pessimistic about future formats. > This is nothing else but normal CPU enablement work - it should be done > when it is really needed. > > Because the opposite can happen: you can add a model check which > excludes future model X, future model X comes along but does *not* > change the RMP format and then you're going to have to relax that model > check again to fix SNP on the new model X. > > So pls add the model checks only when really needed. > > Thx. > > -- > Regards/Gruss, > Boris. > > https://people.kernel.org/tglx/notes-about-netiquette
