Messages in this thread | | | Date | Wed, 24 Feb 2016 19:45:01 +0000 | From | Matt Fleming <> | Subject | Re: [tip:efi/core] x86/mm/pat: Use _PAGE_GLOBAL bit for EFI page table mappings |
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On Wed, 24 Feb, at 10:56:13AM, Linus Torvalds wrote: > On Wed, Feb 24, 2016 at 8:36 AM, Andy Lutomirski <luto@amacapital.net> wrote: > >> > >> So the EFI runtime crap should not change once it is mapped. And those > >> should be global. It is only natural. > > > > Why is it natural? > > > > Long-term, I'd rather see EFI runtime services use an actual mm_struct > > and use_mm. > > Definitely. > > The EFI runtime page mapping may be unchanging, but that doesn't mean > we should be mapping it all the time - the mapping may not change, but > we will change away from it.
There is movement towards hanging the EFI memory map off of mm_struct for x86. ARM and arm64 already do this and there were some patches from Sylvain (Cc'd) to do this for the purposes of having a task context that could be preempted while in the middle of an EFI runtime call for some Intel platforms,
https://lkml.kernel.org/r/1452702762-27216-4-git-send-email-sylvain.chouleur@gmail.com
Apart from the code simplification and not being required to open-code the %cr3 diddling, are there other benefits of mm_struct and use_mm() that make it appealing in the non-preemptible case?
Not that those aren't reasons enough.
> So marking those pages global is very wrong.
Ingo, Andy, how do you want to handle this patch? Maybe just drop it from tip/efi/core while we prod around making all the EFI mappings non-global? Nothing else depends on it, it can be dropped without any harm.
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