From: Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
To: Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Ard Biesheuvel
<ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
Matt Fleming
<matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"Lee, Chun-Yi" <jlee-IBi9RG/b67k@public.gmane.org>,
Borislav Petkov <bp-l3A5Bk7waGM@public.gmane.org>,
Leif Lindholm
<leif.lindholm-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
Peter Jones <pjones-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
James Bottomley <JBottomley-wo1vFcy6AUs@public.gmane.org>,
Matthew Garrett <mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org>,
Dave Young <dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Linus Torvalds
<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>,
Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Denys Vlasenko <dvlasenk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Brian Gerst <brgerst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Subject: Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime
Date: Tue, 29 Sep 2015 14:52:56 +0100 [thread overview]
Message-ID: <20150929135256.GA4401@codeblueprint.co.uk> (raw)
In-Reply-To: <20150929091230.GA2023-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
On Tue, 29 Sep, at 11:12:30AM, Ingo Molnar wrote:
>
> * Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
>
> > > except that I don't think
> > > the condition on 64-bit makes any sense:
> > >
> > > + if (!efi_enabled(EFI_OLD_MEMMAP) && efi_enabled(EFI_64BIT)) {
> > >
> > > I can see us being nervous wrt. backported patches, but is there any strong reason
> > > to not follow this up with a third (non-backported) patch that changes this to:
> > >
> > > + if (!efi_enabled(EFI_OLD_MEMMAP)) {
> > >
> > > for v4.4?
> > >
> >
> > The 32-bit side essentially implements the old memmap only, which is the the
> > bottom-up version. So old memmap will be implied by 32-bit but not set in the
> > EFI flags, resulting in the reverse enumeration being used with the bottom-up
> > mapping logic. The net result of that is that we create the same problem for
> > 32-bit that we are trying to solve for 64-bit, i.e., the regions will end up in
> > reverse order in the VA mapping.
> >
> > To deobfuscate this particular conditional, we could set EFI_OLD_MEMMAP
> > unconditionally on 32-bit x86. Or we could reshuffle variables and conditionals
> > in various other way.
>
> Setting EFI_OLD_MEMMAP would be fine, if doing that has no bad side effects.
Right, I think that's a very good suggestion, because like Ard
mentioned, since EFI_OLD_MEMMAP is implied for 32-bit (there's no
other way to map stuff currently), so it makes sense to force set the
bit.
> > [...] I am not convinced that the overall end result will be any better though.
>
> That's not true, we change an obscure, implicit dependency on 32-bit detail to an
> explicit EFI_OLD_MEMMAP flag that shows exactly what's happening. That's a clear
> improvement.
Agreed.
--
Matt Fleming, Intel Open Source Technology Center
next prev parent reply other threads:[~2015-09-29 13:52 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-25 22:02 [GIT PULL 0/2] EFI urgent fixes Matt Fleming
2015-09-25 22:02 ` [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime Matt Fleming
[not found] ` <1443218539-7610-2-git-send-email-matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2015-09-26 5:56 ` Ingo Molnar
[not found] ` <20150926055643.GA25877-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2015-09-26 6:44 ` Ard Biesheuvel
2015-09-26 17:01 ` Andy Lutomirski
2015-09-26 17:20 ` H. Peter Anvin
[not found] ` <E40EBF14-FD9E-49C0-A7FB-951958F72F79-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2015-09-26 18:15 ` Ard Biesheuvel
2015-09-26 19:49 ` H. Peter Anvin
2015-09-26 19:57 ` Matt Fleming
[not found] ` <20150926195755.GC3144-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2015-09-26 20:09 ` Ard Biesheuvel
2015-09-26 20:19 ` H. Peter Anvin
2015-09-27 16:30 ` Andy Lutomirski
[not found] ` <CALCETrUA6k-oHzuWA54VzEA1v63b5--JPCCuBoOxLisOtjUn+g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-09-27 18:06 ` Matthew Garrett
[not found] ` <20150927180633.GA29466-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org>
2015-09-28 6:16 ` Ingo Molnar
2015-09-28 6:41 ` Matthew Garrett
[not found] ` <20150928064143.GA7380-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org>
2015-09-29 21:58 ` Laszlo Ersek
2015-09-30 9:30 ` Ard Biesheuvel
[not found] ` <CAKv+Gu-enULj-OMRufB3OPSUVueM1843bD1CdFybaAS7xMUKgw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-09-30 16:43 ` Andy Lutomirski
2015-09-30 17:24 ` James Bottomley
[not found] ` <20150928061646.GA21690-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2015-09-30 0:54 ` H. Peter Anvin
2015-09-26 19:55 ` Matt Fleming
2015-09-27 6:50 ` Ingo Molnar
2015-09-26 13:43 ` Matt Fleming
[not found] ` <20150926134329.GA3144-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2015-09-27 7:03 ` Ingo Molnar
2015-09-28 6:49 ` Ard Biesheuvel
[not found] ` <CAKv+Gu8M2pmzfeA=NT4c44E6-PQvRKHZjEJt78mryGcp6bBD8w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-09-28 8:22 ` Ingo Molnar
[not found] ` <20150928082245.GA28796-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2015-09-28 9:51 ` Ard Biesheuvel
2015-09-29 9:12 ` Ingo Molnar
2015-09-29 10:41 ` Ard Biesheuvel
[not found] ` <CAKv+Gu8GpaHRL8EZxJCs8dw8ngFVoYNP1Q=hqhZ=LOF+3vXPLw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-09-29 14:18 ` Matt Fleming
[not found] ` <20150929091230.GA2023-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2015-09-29 13:52 ` Matt Fleming [this message]
2015-09-25 22:02 ` [PATCH 2/2] arm64/efi: Don't pad between EFI_MEMORY_RUNTIME regions Matt Fleming
[not found] ` <1443218539-7610-3-git-send-email-matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2015-09-26 6:01 ` Ingo Molnar
[not found] ` <20150926060159.GB25877-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2015-09-26 7:08 ` Ard Biesheuvel
[not found] ` <CAKv+Gu_JRCmx5qKq7SDDq73BegVs3LKZwe+OdvTKb4YD_CURyw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-09-27 7:06 ` Ingo Molnar
2015-09-27 10:40 ` Borislav Petkov
2015-09-28 6:20 ` Ingo Molnar
2015-09-29 9:31 ` Dave Young
2015-09-29 10:24 ` Borislav Petkov
[not found] ` <20150927104014.GA7631-fF5Pk5pvG8Y@public.gmane.org>
2015-09-29 14:36 ` Matt Fleming
[not found] ` <20150929143612.GC4401-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
2015-09-30 0:56 ` H. Peter Anvin
[not found] ` <560B3327.9020801-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2015-09-30 8:33 ` Borislav Petkov
2015-09-30 1:03 ` H. Peter Anvin
2015-09-30 1:16 ` Andy Lutomirski
2015-09-30 1:19 ` H. Peter Anvin
[not found] ` <CALCETrVvwxZN95swaUDG2fkz9brWV3BQkfMDtLJXZkTRpe8nRg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-09-30 4:24 ` Ard Biesheuvel
2015-10-01 10:44 ` Ingo Molnar
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