Messages in this thread | | | Date | Wed, 2 Mar 2016 11:20:36 +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 Mon, 29 Feb, at 11:56:56AM, Sylvain Chouleur wrote: > 2016-02-24 20:45 GMT+01:00 Matt Fleming <matt@codeblueprint.co.uk>: > > 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 > > I was thinking we could use the efi kthread to handle the efi services > generically, not only for the interruptible case, and have a way to decide if we > allow interruptions inside the efi call itself or not. > > Then all runtime services would use an mm_struct. The drawback is that you will > need two context switchs to be able to execute the runtime service.
I would be surprised if the asynchronous nature of having a special EFI kthread would buy you any benefit in general. And in fact, in the efi-pstore code you can be invoked in IRQ context and you really don't want to start talking to a kthread.
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