linux-kernel - Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime

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Message-ID: <20150926195535.GB3144@codeblueprint.co.uk>
Date:	Sat, 26 Sep 2015 20:55:35 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Matt Fleming <matt.fleming@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"Lee, Chun-Yi" <jlee@...e.com>, Borislav Petkov <bp@...e.de>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Peter Jones <pjones@...hat.com>,
	James Bottomley <JBottomley@...n.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Dave Young <dyoung@...hat.com>,
	stable <stable@...r.kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Brian Gerst <brgerst@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] x86/efi: Map EFI memmap entries in-order at runtime

On Sat, 26 Sep, at 10:20:22AM, H. Peter Anvin wrote:
>
> I think it "works" because the affected BIOSes don't put spaces
> between the chunks.  I have discussed this with Matt.

Right, that's very true. Though note that the current mapping
algorithm will handle a gap <= PMD_SIZE, it's just anything larger
than PMD_SIZE we "squash" to the next multiple of PMD_SIZE.

It's unclear whether the firmware toolchains would even support
references between sections with a PMD_SIZE gap between them, and I
think the firmware engineers would have to go out of their way to
actually insert such a gap.

-- 
Matt Fleming, Intel Open Source Technology Center
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