linux-kernel - Re: [PATCH -v2 0/4] EFI 1:1 mapping

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Message-ID: <51C3738E.3070901@zytor.com>
Date:	Thu, 20 Jun 2013 14:26:38 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Matthew Garrett <mjg59@...f.ucam.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux EFI <linux-efi@...r.kernel.org>,
	Matt Fleming <matt@...sole-pimps.org>, X86 ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH -v2 0/4] EFI 1:1 mapping

On 06/19/2013 09:59 AM, Borislav Petkov wrote:
> On Wed, Jun 19, 2013 at 05:48:22PM +0100, Matthew Garrett wrote:
>>> Ok, so it sounds like we want to *always* create both mappings but,
>>> depending on what we want, to shove down SetVirtualAddressMap a
>>> different set. And the 1:1 map will be the optional one which we give
>>> SetVirtualAddressMap only when user wants it, i.e. when booting with
>>> "efi=1:1_map".
>>
>> Yup, I think that sounds ideal.
> 
> Crap, I got completely sidetracked. The 1:1 mappings go in a different
> pagetable (real_mode_header->trampoline_pgd) than the kernel one
> (i.e. init_mm.pgd). However, the ->trampoline_pgd has all mappings
> anyway, which means that if we want to do EFI runtime calls with the
> high mappings but *also* have the 1:1 mappings established, we should
> *always* switch to that pagetable when doing those calls.
> 
> hpa, MattF, agreed?
> 

Yes.

	-hpa

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