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

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Message-ID: <20130603162435.GA22563@srcf.ucam.org>
Date:	Mon, 3 Jun 2013 17:24:35 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	Borislav Petkov <bp@...en8.de>,
	Linux EFI <linux-efi@...r.kernel.org>,
	Matt Fleming <matt@...sole-pimps.org>,
	Jiri Kosina <jkosina@...e.cz>, X86-ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH 0/4] EFI 1:1 mapping

On Mon, Jun 03, 2013 at 09:18:06AM -0700, James Bottomley wrote:

> I don't entirely buy that.  All EFI programs run with the physical
> address map, therefore every API an EFI program uses is also tested, at
> boot time only, obviously.

That seems optimistic. Windows never calls QueryVariableInfo() during 
boot services, so what makes you think doing so has ever been tested?

> However, the ExitBootServices() code seems to be much simpler, so I 
> don't think it will cause too many bugs.  The UEFI test suites also 
> seem to try UEFI calls before and after ExitBootServices(), so I think 
> relying on a 1:1 mapping looks safer to me.

I have no expectation that the majority of system vendors run the test 
suite, but I have every expectation that every system vendor runs 
Windows. We should behave as close to the tested mechanism as possible, 
ie do what Windows does - and that includes calling 
SetVirtualAddressMap().

-- 
Matthew Garrett | mjg59@...f.ucam.org
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