linux-kernel - Calgary and bad_dma

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Date:	Tue, 9 Sep 2008 21:19:41 -0600
From:	Pete Zaitcev <zaitcev@...hat.com>
To:	<jdmason@...zu.us>, <muli@...ibm.com>
Cc:	zaitcev@...hat.com, linux-kernel@...r.kernel.org
Subject: Calgary and bad_dma_address

Hi, guys:

I was reading arch/x86/kernel/pci-calgary_64.c today, and noticed that
apparently nothing prevents iommu_area_alloc from returning a zero.
But bad_dma_address is zero too. Doesn't it concern anyone?
If the first allocation asks for a page-aligned buffer to be mapped,
a spurious bad address will result, if I understand this right.

The simplest way to avoid the problem is to lose a page and set a bit
in tce_table_setparms():
   set_bit(tbl->it_map, bad_dma_address);
But I don't see anything like that done anywhere.

-- Pete
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