From: David Mosberger <davidm@napali.hpl.hp.com>
To: "David S. Miller" <davem@redhat.com>
Cc: davidm@hpl.hp.com, manfred@colorfullife.com, axboe@suse.de,
linux-kernel@vger.kernel.org
Subject: Re: problem with blk_queue_bounce_limit()
Date: Sat, 7 Jun 2003 00:05:06 -0700 [thread overview]
Message-ID: <16097.36514.763047.738847@napali.hpl.hp.com> (raw)
In-Reply-To: <20030606.234401.104035537.davem@redhat.com>
>>>>> On Fri, 06 Jun 2003 23:44:01 -0700 (PDT), "David S. Miller" <davem@redhat.com> said:
DaveM> But on an IOMMU system, we could end up mapping to the same
DaveM> bogus DMA address.
Ah, yes, just changing the buffer address doesn't guarantee a
different bus address. I missed that.
DaveM> So we have to solve this problem by keeping the existng bad
DaveM> mapping, doing a new DMA mapping, then trowing away the old
DaveM> one.
But you're creating a new mapping for the old buffer. What if you had
a DMA API implementation which consolidates multiple mapping attempts
of the same buffer into a single mapping entry (along with a reference
count)? That would break the workaround.
Isn't the proper fix to (a) get a new buffer, (b) create a mapping for
the new buffer, (c) destroy the mapping for the old buffer. That
should guarantee a different bus address, no matter what the
DMA-mapping implementation.
Plus then you don't have to rely on PCI_DMA_BUS_IS_PHYS.
--david
next prev parent reply other threads:[~2003-06-07 6:51 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-06-05 6:42 problem with blk_queue_bounce_limit() David Mosberger
2003-06-05 7:20 ` David S. Miller
2003-06-06 6:42 ` David Mosberger
2003-06-06 6:45 ` David S. Miller
2003-06-06 6:54 ` David Mosberger
2003-06-06 7:08 ` David S. Miller
2003-06-06 6:52 ` David S. Miller
2003-06-06 7:19 ` David Mosberger
2003-06-06 7:32 ` David S. Miller
2003-06-06 7:44 ` Christoph Hellwig
2003-06-06 7:43 ` David S. Miller
2003-06-06 7:51 ` Christoph Hellwig
2003-06-06 20:13 ` David Mosberger
2003-06-07 6:44 ` David S. Miller
2003-06-07 7:05 ` David Mosberger [this message]
2003-06-07 7:11 ` David S. Miller
2003-06-10 20:01 ` David Mosberger
2003-06-12 6:47 ` David S. Miller
2003-06-15 7:06 ` Anton Blanchard
2003-06-15 7:11 ` David S. Miller
2003-06-15 8:04 ` Anton Blanchard
2003-06-15 8:18 ` David S. Miller
2003-06-07 7:20 ` David Mosberger
2003-06-07 7:19 ` David S. Miller
2003-06-07 9:44 ` Russell King
2003-06-07 9:47 ` David S. Miller
2003-06-07 13:23 ` Christoph Hellwig
2003-06-10 20:24 ` David Mosberger
2003-06-06 18:06 James Bottomley
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