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From: "David S. Miller" <davem@redhat.com>
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Date: Fri, 29 Jun 2001 02:16:14 -0700 (PDT)
To: Jes Sorensen <jes@sunsite.dk>
Cc: Ben LaHaise <bcrl@redhat.com>,
        "MEHTA,HIREN (A-SanJose,ex1)" <hiren_mehta@agilent.com>,
        "'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>
Subject: Re: (reposting) how to get DMA'able memory within 4GB on 64-bit m achi ne
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Jes Sorensen writes:
 > Thats easy
 ...
 > This way you automatically get support for the situation Ben mentioned
 > as well, when doing large allocs and the IOMMU is full you return a
 > full 64 bit address.

And when the IOMMU is "full" what happens to all the SAC only
cards in the machine?  pci_map_{single,sg}() are not allowed
to fail.

See, it's not so easy.

Later,
David S. Miller
davem@redhat.com