linux-kernel - Re: [sodaville] [PATCH] x86/trampoline: fallback to fixed trampoline address if no e820 map is provided

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Message-ID: <4D139A4C.7000003@linux.intel.com>
Date:	Thu, 23 Dec 2010 10:51:56 -0800
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Yinghai <yinghai@...nel.org>
CC:	Florian Fainelli <ffainelli@...ebox.fr>,
	"sodaville@...utronix.de" <sodaville@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [sodaville] [PATCH] x86/trampoline: fallback to fixed	trampoline
 address if no e820 map is provided

On 12/23/2010 05:16 AM, Yinghai wrote:
> 
> On Dec 23, 2010, at 1:57 AM, Florian Fainelli <ffainelli@...ebox.fr> wrote:
> 
>> On Tuesday 14 December 2010 22:19:39 Florian Fainelli wrote:
>>> From: Florian Fainelli <ffainelli@...ebox.fr>
>>>
>>> Since 893f38d1 (x86: Use find_e820() instead of hard coded trampoline
>>> address), the trampoline base address should be provided by the BIOS as an
>>> e820 area. Some minimalistic BIOSes (like CEFDK on CE4100) may not provide
>>> any e820 area, still we should fallback to a fixed trampoline base address
>>> for SMP to work correctly.
> 
> No e820 memmap ?
> 
> Not sure how does it work
> 
> Do you have boot log with debug ?
> 
> Also recent kernel is using memblock already for finding free area.
> 

OK, this deeply troubles me.  This is clearly not the right approach
here... the memory map should be fed to the kernel, this has been a
requirement all along, and Linus has very deliberately not agreed to
exceptions (and I agree with that stance.)

So this patch is a non-starter... I presume the memory map is being
provided in through the device (which means it should be fed into
memblock in current kernels, although the ordering may need to be tweaked?)

	-hpa
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