On 14/05/2024 14:43, Conor Dooley wrote: > 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... No worries, I was on vacation and was just checking if I hadn't missed anything in the meantime. Take your time ;) Thanks, Clément
