On Tue, May 14, 2024 at 09:53:08AM +0200, Clément Léger wrote: > > > On 30/04/2024 13:44, Conor Dooley wrote: > > On Tue, Apr 30, 2024 at 09:18:47AM +0200, Clément Léger wrote: > >> > >> > >> On 30/04/2024 00:15, Conor Dooley wrote: > >>> On Mon, Apr 29, 2024 at 05:04:55PM +0200, Clément Léger wrote: > >>>> Since a few extensions (Zicbom/Zicboz) already needs validation and > >>>> future ones will need it as well (Zc*) add a validate() callback to > >>>> struct riscv_isa_ext_data. This require to rework the way extensions are > >>>> parsed and split it in two phases. First phase is isa string or isa > >>>> extension list parsing and consists in enabling all the extensions in a > >>>> temporary bitmask without any validation. The second step "resolves" the > >>>> final isa bitmap, handling potential missing dependencies. The mechanism > >>>> is quite simple and simply validate each extension described in the > >>>> temporary bitmap before enabling it in the final isa bitmap. validate() > >>>> callbacks can return either 0 for success, -EPROBEDEFER if extension > >>>> needs to be validated again at next loop. A previous ISA bitmap is kept > >>>> to avoid looping mutliple times if an extension dependencies are never > >>>> satisfied until we reach a stable state. In order to avoid any potential > >>>> infinite looping, allow looping a maximum of the number of extension we > >>>> handle. Zicboz and Zicbom extensions are modified to use this validation > >>>> mechanism. > >>> > >>> Your reply to my last review only talked about part of my comments, > >>> which is usually what you do when you're gonna implement the rest, but > >>> you haven't. > >>> I like the change you've made to shorten looping, but I'd at least like > >>> a response to why a split is not worth doing :) > >> > >> Hi Conor, > >> > >> Missed that point since I was feeling that my solution actually > >> addresses your concerns. Your argument was that there is no reason to > >> loop for Zicbom/Zicboz but that would also apply to Zcf in case we are > >> on RV64 as well (since zcf is not supported on RV64). So for Zcf, that > >> would lead to using both mecanism or additional ifdefery with little to > >> no added value since the current solution actually solves both cases: > >> > >> - We don't have any extra looping if all validation callback returns 0 > >> (except the initial one on riscv_isa_ext, which is kind of unavoidable). > >> - Zicbom, Zicboz callbacks will be called only once (which was one of > >> your concern). > >> > >> Adding a second kind of callback for after loop validation would only > >> lead to a bunch of additional macros/ifdefery for extensions with > >> validate() callback, with validate_end() or with both (ie Zcf)). For > >> these reasons, I do not think there is a need for a separate mechanism > >> nor additional callback for such extensions except adding extra code > >> with no real added functionality. > >> > >> AFAIK, the platform driver probing mechanism works the same, the probe() > >> callback is actually called even if for some reason properties are > >> missing from nodes for platform devices and thus the probe() returns > >> -EINVAL or whatever. > >> > >> Hope this answers your question, > > > > Yeah, pretty much I am happy with just an "it's not worth doing it" > > response. Given it wasn't your first choice, I doubt you're overly happy > > with it either, but I really would like to avoid looping to closure to > > sort out dependencies - particularly on the boot CPU before we bring > > anyone else up, but if the code is now more proactive about breaking > > out, I suppose that'll have to do :) > > I kinda wish we didn't do this at all, but I think we've brought this > > upon ourselves via hwprobe. I'm still on the fence as to whether things > > that are implied need to be handled in this way. I think I'll bring this > > up tomorrow at the weekly call, because so far it's only been you and I > > discussing this really and it's a policy decision that hwprobe-ists > > should be involved in I think. > > Hi Conor, > > Were you able to discuss that topic ? I realised last night that I'd not got back to this thread and meant to do that today (I had accidentally deleted it from my mailbox), but I had a migraine this morning and so didn't. I did bring it up and IIRC Palmer was of the opinion that we should try our best to infer extensions. > > Implied extensions aside, I think we will eventually need this stuff > > anyway, for extensions that make no sense to consider if a config option > > for a dependency is disabled. > > From talking to Eric Biggers the other week about > > riscv_isa_extension_available() I'm of the opinion that we need to do > > better with that interface w.r.t. extension and config dependencies, > > and what seems like a good idea to me at the moment is putting tests for > > IS_ENABLED(RISCV_ISA_FOO) into these validate hooks. > > > > I'll try to look at the actual implementation here tomorrow. > > Did you found time to look at the implementation ? No, with the above excuse. I'll try to get to it today or tomorrow...
Attachment:
signature.asc
Description: PGP signature
