Re: [PATCH 2/2] arm64/efi: Don't pad between EFI_MEMORY_RUNTIME regions

From: Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: Matt Fleming
	<matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>,
	Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
	"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@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>,
	Leif Lindholm
	<leif.lindholm-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>,
	Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>,
	"stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Matt Fleming
	<matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>,
	Mark Salter <msalter-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Linus Torvalds
	<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>,
	Denys Vlasenko <dvlasenk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Brian Gerst <brgerst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 2/2] arm64/efi: Don't pad between EFI_MEMORY_RUNTIME regions
Date: Sun, 27 Sep 2015 09:06:44 +0200	[thread overview]
Message-ID: <20150927070644.GC26125@gmail.com> (raw)
In-Reply-To: <CAKv+Gu_JRCmx5qKq7SDDq73BegVs3LKZwe+OdvTKb4YD_CURyw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

* Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.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