linux-kernel - Re: [PATCH] x86: fix system die when load with "reservetop" parameter

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Message-ID: <20090821133553.GE10263@elte.hu>
Date:	Fri, 21 Aug 2009 15:35:53 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Yinghai Lu <yinghai@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org
Subject: Re: [PATCH] x86: fix system die when load with "reservetop"
	parameter


* Xiao Guangrong <xiaoguangrong@...fujitsu.com> wrote:

> The system will die if the kernel is booted with "reservetop" 
> parameter, in present code, parse "reservetop" parameter after 
> early_ioremap_init(), and some function still use early_ioremap() 
> after it.

btw., what are you using the 'reservetop' boot option for?

> The problem is, "reservetop" parameter can modify 'FIXADDR_TOP', 
> then the virtual address got by early_ioremap() is base on old 
> 'FIXADDR_TOP', but the page mapping is base on new 'FIXADDR_TOP', 
> it will occur page fault, and the IDT is not prepare yet, so, the 
> system is dead.
> 
> So, put parse_early_param() in the front of early_ioremap_init() 
> in this patch.
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> ---
>  arch/x86/kernel/setup.c |   10 +++++-----
>  1 files changed, 5 insertions(+), 5 deletions(-)

Does this bug trigger in 2.6.30 too?

I'm quite nervous about doing this change so late in the .31 cycle, 
we've got a hundred early parameters that now get executed much 
earlier than before. No way can i test all of them and others 
testing it (like in your case) takes time to trickle through.

So unless this is a .31 regression i'd be inclined to queue it up 
for .32.

	Ingo
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