linux-kernel - Re: [PATCH v3] x86, efi: Calling __pa() with an ioremap'd address is invalid

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Message-ID: <20111107202324.GA27515@srcf.ucam.org>
Date:	Mon, 7 Nov 2011 20:23:24 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, Zhang Rui <rui.zhang@...el.com>,
	Huang Ying <huang.ying.caritas@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] x86, efi: Calling __pa() with an ioremap'd address
 is invalid

On Mon, Nov 07, 2011 at 03:34:48PM +0000, Matt Fleming wrote:

> After the feedback from v1 I tried to unify the efi_ioremap()
> implementations but ran into the issue detailed in the RH bug report
> in the changelog. Unless we teach the x86 setup code that
> EFI_RUNTIME_SERVICES_DATA regions should be part of the direct kernel
> mapping table (even though they're marked as E820_RESERVED) I think
> this patch makes the most sense.

Honestly it seems like there may well be an argument for that. We're 
talking about executable code that the kernel will be calling - it seems 
theoretically neater for it to be added to the direct mapping. We're 
just heavily constrained by our collapsing of the EFI memory map onto 
the rather less fine-grained E820 one and the lack of any obvious way to 
extend that in an OS-specific manner. I guess we could expect the 
bootloader to conform to the standard and then re-walk the EFI memory 
map ourselves to fix things up, but eww...

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