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Date: Sun, 09 Sep 2012 09:56:17 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Suresh Siddha <suresh.b.siddha@intel.com>,
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        Andrew Morton <akpm@linux-foundation.org>, dwmw2@infradead.org,
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        linux-mtd@lists.infradead.org, linux-mm <linux-mm@kvack.org>,
        Dave Jones <davej@redhat.com>
Subject: Re: mtd: kernel BUG at arch/x86/mm/pat.c:279!
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On 09/08/2012 12:57 PM, Linus Torvalds wrote:
>
> Ack.
>
> Anyway, that means that the BUG_ON() is likely bogus, but so is the
> whole calling convention.
>
> The 4kB range starting at 0xfffffffffffff000 sounds like a *valid*
> range, but that requires that we fix the calling convention to not
> have that "end" (exclusive) thing. It should either be "end"
> (inclusive), or just "len".
>

On x86, it is definitely NOT a valid range.  There is no physical 
addresses there, and there will never be any.

> So it should either be start=0xfffffffffffff000 end=0xffffffffffffffff
> or it should be start=0xfffffffffffff000 len=0x1000.

I would strongly object to the former; that kind of inclusive ranges 
breed a whole class of bugs by themselves.

	-hpa

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