linux-kernel - Re: [PATCH] x86/boot: Reorganize and clean up the BIOS area reservation code

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Message-ID: <20160721161807.GB30106@gmail.com>
Date:	Thu, 21 Jul 2016 18:18:07 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Matt Fleming <mfleming@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mario Limonciello <mario_limonciello@...l.com>,
	Kees Cook <keescook@...omium.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] x86/boot: Reorganize and clean up the BIOS area
 reservation code


* Andy Lutomirski <luto@...capital.net> wrote:

> It would be very easy to implement this if we could handle overlapping memblocks 
> precisely or set a lower limit on the memblock allocator. Then we could block 
> off everything below 1MB or 2MB very early and then unblock it or temporarily 
> change the lower limit and ask for a single page for the trampoline after that.

So my suggestion was/is to _permanently_ allocate the SMP trampoline page, and 
leave it also reserved.

'Reserving' a memory area is really just a kernel internal matter. We can still 
use it. No need to unreserve/allocate/re-reserve ... unless I'm missing something.

Thanks,

	Ingo