From: Tejun Heo <tj@kernel.org>
To: Michal Simek <monstr@monstr.eu>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Yinghai Lu <yinghai@kernel.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Sam Ravnborg <sam@ravnborg.org>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: memblock and bootmem problems if start + size = 4GB
Date: Mon, 19 Dec 2011 08:28:35 -0800 [thread overview]
Message-ID: <20111219162835.GA24519@google.com> (raw)
In-Reply-To: <4EEF42F5.7040002@monstr.eu>
Hello, Michal.
On Mon, Dec 19, 2011 at 02:58:13PM +0100, Michal Simek wrote:
> I have reached some problems with memblock and bootmem code for some configurations.
> We can completely setup the whole system and all addresses in it.
> The problem happens if we place main memory to the end of address space when
> mem_start + size reach 4GB limit.
>
> For example:
> mem_start 0xF000 0000
> mem_size 0x1000 0000 (or better lowmem size)
> mem_end 0xFFFF FFFF
> start + size 0x1 0000 0000 (u32 limit reached).
>
> I have done some patches which completely remove start + size values from architecture specific
> code but I have found some problem in generic code too.
>
> For example in bootmem code where are three places where physaddr + size is used.
> I would prefer to retype it to u64 because baseaddr and size don't need to be 2^n.
>
> Is it correct solution? If yes, I will create proper patch.
Yeah, that's an inherent problem in using [) ranges but I think
chopping off the last page probably is simpler and more robust
solution. Currently, memblock_add_region() would simply ignore if
address range overflows but making it just ignore the last page is
several lines of addition. Wouldn't that be effective enough while
staying very simple?
Thanks.
--
tejun
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next prev parent reply other threads:[~2011-12-19 16:28 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-19 13:58 memblock and bootmem problems if start + size = 4GB Michal Simek
2011-12-19 16:28 ` Tejun Heo [this message]
2011-12-20 9:19 ` Michal Simek
2011-12-29 13:44 ` Michal Simek
2011-12-29 15:58 ` Tejun Heo
2011-12-29 16:46 ` Michal Simek
2011-12-29 17:07 ` Tejun Heo
2011-12-30 7:58 ` Michal Simek
2011-12-30 17:45 ` Tejun Heo
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