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From: Chuck Ebbert <cebbert@redhat.com>
To: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: hancockrwd@gmail.com, ak@linux.intel.com,
	linux-kernel@vger.kernel.org, dwmw2@infradead.org
Subject: Re: b44 driver causes panic when using swiotlb
Date: Tue, 1 Feb 2011 16:18:59 -0500	[thread overview]
Message-ID: <20110201161859.467676b0@katamari> (raw)
In-Reply-To: <20110201102707C.fujita.tomonori@lab.ntt.co.jp>

On Tue, 1 Feb 2011 10:28:00 +0900
FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:

> 
> swiotlb allocates the bounce buffer when a system boots up. We can't
> allocate much in GFP_DMA. swiotlb uses somewhere under 4GB. So it
> can't help devices that have odd dma_mask (that is, except for 4GB).
> 
> Unfortunately, Such device needs to do own custom bouncing or needs
> their subsystem to does that.

I think we're chasing the wrong problem here.

swiotlb uses alloc_bootmem_low_pages() to try to get buffers as low
in memory as possible. I asked someone who is hitting this bug to
try 2.6.36 and he reports the buffers really are low there:

2.6.36:  5c00000
2.6.37: db600000

So something happened very early in the 2.6.37-rc cycle that changed
this behavior. I tried looking at the bootmem code but could not see
the problem. The only related option I could find in .config was this:

# CONFIG_NO_BOOTMEM is not set

It was set this way in both .36 and .37.

  parent reply	other threads:[~2011-02-01 21:22 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-31 15:54 Chuck Ebbert
2011-01-31 16:36 ` Andi Kleen
2011-02-01  0:54   ` Robert Hancock
2011-02-01  1:28     ` FUJITA Tomonori
2011-02-01  3:22       ` Robert Hancock
2011-02-01  5:22         ` FUJITA Tomonori
2011-02-15  0:47           ` Robert Hancock
2011-02-01 21:18       ` Chuck Ebbert [this message]
2011-02-02  0:06         ` FUJITA Tomonori
2011-02-02  0:09           ` FUJITA Tomonori
2011-02-01 18:07     ` Andi Kleen
2011-02-01 21:44       ` Robert Hancock
2011-02-01 13:54 ` FUJITA Tomonori
2011-02-14 11:59   ` FUJITA Tomonori
2011-02-14 16:41     ` Arkadiusz Miśkiewicz
2011-02-15  0:39       ` FUJITA Tomonori
2011-02-15 22:03     ` Chuck Ebbert
     [not found] <4D478EDC.4070004@lwfinger.net>
2011-02-01  4:53 ` Larry Finger

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