linux-kernel - Re: [PATCH 31/31] memblock: Add memblock_find_in

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Message-ID: <4C4FD04B.5090503@zytor.com>
Date:	Tue, 27 Jul 2010 23:38:03 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 31/31] memblock: Add memblock_find_in_range()

On 07/27/2010 11:08 PM, Yinghai Lu wrote:
> 
> for example: 
> high/low allocation, from first kernel to kexec second kernel, always work fine except system with Qlogic card.
> because Qlogic card is using main RAM as EFT etc for card's FW log trace. second kernel have not idea that those RAM
>  is used by first kernel for that purpose. that the CARD still use that between two kernels.
> second kernel could have crash it try to use those ram.
> 

Uhm, no.  That's a bug in the Qlogic driver not shutting the card down
cleanly.  Hacking around that in memory allocation order is braindamaged
in the extreme.  kexec *cannot* be safe in any way if we don't shut down
pending DMA, and what you describe above is DMA.

> low/high allocation seems to be safe,  second kernel can slip to boot fine.

Low to high is just broken.  Low memory is a special, desirable
resource, and we should minimize the use of it.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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