linux-kernel - Re: [PATCH] x86_64/efi: Mapping Boot and Runtime EFI memory regions to different starting virtual address

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Message-ID: <20150730101131.GB2725@codeblueprint.co.uk>
Date:	Thu, 30 Jul 2015 11:11:31 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Borislav Petkov <bp@...en8.de>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	"Lee, Chun-Yi" <joeyli.kernel@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Lee, Chun-Yi" <jlee@...e.com>
Subject: Re: [PATCH] x86_64/efi: Mapping Boot and Runtime EFI memory regions
 to different starting virtual address

On Thu, 30 Jul, at 10:03:23AM, Borislav Petkov wrote:
> On Thu, Jul 30, 2015 at 12:53:42AM -0700, H. Peter Anvin wrote:
> > This changelog is at least partially incomprehensive. It also seems
> > more than a bit aggressive to expect that 1 GB will be sufficient
> > forever.
> 
> Right, before we do anything, I'd like for us to figure out first why
> this is a problem all of a sudden. And why should we even keep boot
> code/data, if it is fair game, once runtime services get enabled.
> 
> Matt, can you please chime in first before we even talk about a
> solution...

Yeah, I do not understand the issue properly.

Why do we care about EfiBoot* regions after hibernate? Surely we've
already freed those regions in efi_free_boot_services() during boot and
nobody should be touching them again? If the firmware does, that's a
whole new bug we've never encountered before.

And we obviously can't allow the runtime regions to move around during
hibernate/resume because we've already informed the firmware where those
regions live during SetVirtualAddressMap() at boot.

I admit that I haven't looked at the hibernate code paths. Let me go do
that now.

-- 
Matt Fleming, Intel Open Source Technology Center
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