linux-kernel - Re: mtd: kernel BUG at arch/x86/mm/pat.c:279!

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Date:	Sun, 09 Sep 2012 07:56:40 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Sasha Levin <levinsasha928@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>, dwmw2@...radead.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mtd@...ts.infradead.org, linux-mm <linux-mm@...ck.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: mtd: kernel BUG at arch/x86/mm/pat.c:279!

On Sat, 2012-09-08 at 12:57 -0700, Linus Torvalds wrote:
> Whatever. Something like this (TOTALLY UNTESTED) attached patch should
> get the mtdchar overflows to go away, 

It looks good to me. Acked-by: Suresh Siddha <suresh.b.siddha@...el.com>

Sasha, can you please give this a try?

> but it does *not* fix the fact
> that the MTRR start/end model is broken. It really is technically
> valid to have a resource_size_t range of 0xfffffffffffff000+0x1000,
> and right now it causes a BUG_ON() in pat.c.
> 
> Suresh?

yes but that is not a valid range I think because of the supported
physical address bit limits of the processor and also the max
architecture limit of 52 address bits.

I guess we should be checking for those limits in pat.c, especially bits
above 52 are ignored by the HW and they can easily cause conflicting
aliases with other valid regions. I will get back with a different patch
to fix this.

thanks,
suresh

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