linux-kernel - Re: [PATCH v3 03/13] arm64: improve CONFIG_STRICT

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Message-ID: <20141125174800.GA3938@pd.tnic>
Date:	Tue, 25 Nov 2014 18:48:00 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	leif.lindholm@...aro.org, roy.franz@...aro.org,
	linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
	msalter@...hat.com, dyoung@...hat.com, linux-efi@...r.kernel.org,
	matt.fleming@...el.com, will.deacon@....com,
	catalin.marinas@....com, grant.likely@...aro.org,
	geoff.levand@...aro.org, linux-kernel@...r.kernel.org,
	Peter Jones <pjones@...hat.com>
Subject: Re: [PATCH v3 03/13] arm64: improve CONFIG_STRICT_DEVMEM handling

On Tue, Nov 25, 2014 at 05:39:25PM +0000, Matt Fleming wrote:
> On Tue, 18 Nov, at 01:57:02PM, Ard Biesheuvel wrote:
> > Improve the handling of /dev/mem mappings under CONFIG_STRICT_DEVMEM by:
> > - allowing read-only access to parts of System RAM that are not
> >   considered memory by the kernel, this is mainly intended for exposing
> >   UEFI Configuration tables to userland;
> > - avoid using non-cached mappings for those parts of System RAM, as it
> >   may result in mismatched attributes.
> 
> Is this really the best way to expose EFI config tables?
> 
> We already have parts in /sys/firmware/efi/ and in particular we expose
> the runtime mappings there for kexec on x86.

Yeah!

> Hooking this into the /dev/mem infrastructure just seems wrong to me.

And this virtmap.c thing is arm-only, AFAICT, but it looks like generic
code and like a wholly new way of doing the efi page table.

This thing needs to be properly split into generic pieces which go into
drivers/firmware/efi/ and arm-specific which would make that EFI_VIRTMAP
into an arch bit.

And so on and so on...

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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