On Tue, Feb 01, 2022 at 10:58:03AM +0200, Mike Rapoport wrote: > On Mon, Jan 31, 2022 at 12:07:29AM -0800, Michel Lespinasse wrote: > > On Sun, Jan 30, 2022 at 11:13:26AM +0200, Mike Rapoport wrote: > > > The speculative page fault implementation here (and for PowerPC as well) > > > looks very similar to x86. Can we factor it our rather than copy 3 (or > > > more) times? > > > > In each arch, the speculative code was written along the lines of the > > existing non-speculative code, so that behavior would be unchanged > > when speculation succeeds. > > > > Now each arch's existing, non-speculative code paths are quite similar, > > but they do have small differences as to how they implement various > > permission checks, protection keys and the like. The same small > > differences end up being reflected in the new speculative code paths. > > > > I agree it would be nice if this code could be unified between archs, > > but IMO this should start with the existing non-speculative code - > > I don't think it would make sense to try unifying the new speculative > > code while trying to follow the behavior of the non-unified old > > non-speculative code paths... > > Then maybe this unification can be done as the ground work for the > speculative page fault handling? I feel like this is quite unrelated, and that introducing such artificial dependencies is a bad work habit we have here in linux MM... That said, unifying the PF code between archs would be an interesting project on its own. The way I see it, there could be a unified page fault handler, with some arch specific parts defined as inline functions. I can see myself making an x86/arm64/powerpc initial proposal if there is enough interest for it, but I'm not sure how extending it to more exotic archs would go - I think this would have to involve arch maintainers at least for testing purposes, and I'm not sure if they'd have any bandwidth for such a project... -- Michel "walken" Lespinasse
