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Message-ID: <20150927070644.GC26125@gmail.com>
Date: Sun, 27 Sep 2015 09:06:44 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Matt Fleming <matt@...eblueprint.co.uk>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
Leif Lindholm <leif.lindholm@...aro.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
"stable@...r.kernel.org" <stable@...r.kernel.org>,
Matt Fleming <matt.fleming@...el.com>,
Mark Rutland <mark.rutland@....com>,
Mark Salter <msalter@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>,
Borislav Petkov <bp@...en8.de>,
Denys Vlasenko <dvlasenk@...hat.com>,
Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH 2/2] arm64/efi: Don't pad between EFI_MEMORY_RUNTIME
regions
* Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:
> > If we allocate the EFI runtime as a single virtual memory block then issues
> > like rounding between sections does not even come up as a problem: we map the
> > original offsets and sizes byte by byte.
>
> Well, by that reasoning, we should not call SetVirtualAddressMap() in the first
> place, and just use the 1:1 mapping UEFI uses natively. This is more than
> feasible on arm64, and I actually fought hard against using
> SetVirtualAddressMap() at all, but I was overruled by others. I think this is
> also trivially possible on X64, since the 1:1 mapping is already active
> alongside the VA mapping.
Could we please re-list all the arguments pro and contra of 1:1 physical mappings,
in a post that also explains the background so that more people can chime in, not
just people versed in EFI internals? It's very much possible that a bad decision
was made.
Thanks,
Ingo
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