On Mon, 2016-10-03 at 19:09 -0700, Andy Lutomirski wrote: > > Having two separate status booleans for "registers valid" > > and "memory valid" may make more sense. > > I have no problem with the concept of "owner_ctx", and I think it's a > perfectly reasonable data structure. My problem with it is that it's > subtle and knowledge of it is spread all over the place. Just going > with "registers valid" in a variable won't work, I think, because > there's nowhere to put it. We need to be able to delete a struct fpu > while that struct fpu might have a valid copy in a different cpu's > registers. > > Anyway, feel free to tell me that I'm making this too difficult :)
How about we rename fpu_want_lazy_restore to fpu_registers_valid()? Problem solved :) Then we can rename __cpu_disable_lazy_restore to fpu_invalidate_registers(), and call that before we modify any in-memory FPU state. > > We can get rid of fpu.counter, since nobody uses it > > any more. > > We should definitely do this. > > Maybe getting in some cleanups first (my lazy fpu deletion, > fpu.counter removal, etc) first is the way to go. Sounds good. I will keep my patch 1/4 as part of the cleanup series, and will not move on to the harder stuff until after the cleanups. Any other stuff I should clean up while we're there? > > > > > > > You are right, read_pkru() and write_pkru() can only deal with > > the pkru state being present in registers. Is this because of an > > assumption in the code, or because of a hardware requirement? read_pkru and write_pkru would be candidates for using fpu_registers_valid, and potentially a fpu_make_registers_valid, which restores the contents of the fpu registers from memory, if fpu_registers_valid is not true. Likewise, we can have an fpu_make_memory_valid to ensure the in kernel memory copy of the FPU registers is valid, potentially a _read and _write version that do exactly what the pstate code wants today. Would that make sense as an API? -- All Rights Reversed.
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