From: James Bottomley <James.Bottomley@steeleye.com>
To: Grant Grundler <grundler@parisc-linux.org>
Cc: Jens Axboe <axboe@suse.de>,
ak@suse.de, davem@redhat.com, suparna@in.ibm.com,
Linux Kernel <linux-kernel@vger.kernel.org>,
Alex Williamson <alex_williamson@hp.com>,
Bjorn Helgaas <bjorn_helgaas@hp.com>
Subject: Re: [RFC] block layer support for DMA IOMMU bypass mode
Date: 02 Jul 2003 10:52:38 -0500 [thread overview]
Message-ID: <1057161166.1972.19.camel@mulgrave> (raw)
In-Reply-To: <20030701230147.GI14683@dsl2.external.hp.com>
On Tue, 2003-07-01 at 18:01, Grant Grundler wrote:
> > The bio layer works with
> > a nice finite list of generic or per-queue constraints; it doesn't care
> > currently what the underlying device or IOMMU does.
>
> I don't agree. This whole discussion revolves around getting BIO code and
> IOMMU code to agree on how block merging works for a given platform.
> Using a callback into IOMMU code means the BIO truly doesn't have to know.
> The platform specific IOMMU could just tell BIO code what it wants to
> know (how many SG entries would fit into a limited number of physical
> mappings).
Ah, but the point is that currently the only inputs the IOMMU has to the
bio layer are parameters. I'd like to keep it this way unless there's a
really, really good reason not to. At the moment it seems that the
proposed parameter covers all of IA64's needs and may cover AMD64's as
well.
> > Putting such a callback in would add this entanglement.
>
> yes, sort of. But I think this entanglement is present even for machines
> that don't have an IOMMU because of bounce buffers. But if ia64's swiotlb
> would be made generic to cover buffer bouncing....
Well, not to get into the "where should ZONE_NORMAL end" argument again,
but I was hoping that GFP_DMA32 would elminate the IA64 platform's need
for this. __blk_queue_bounce() strikes me as being much more heavily
exercised than the swiotlb, so I think it should be the one to remain.
It also has more context information to fail gracefully.
James
next prev parent reply other threads:[~2003-07-02 15:38 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-01 16:46 [RFC] block layer support for DMA IOMMU bypass mode James Bottomley
2003-07-01 17:09 ` Andi Kleen
2003-07-01 17:28 ` James Bottomley
2003-07-01 17:42 ` Andi Kleen
2003-07-01 19:22 ` Grant Grundler
2003-07-01 19:56 ` James Bottomley
2003-07-01 17:54 ` H. Peter Anvin
2003-07-01 19:19 ` Grant Grundler
2003-07-01 19:59 ` Alex Williamson
2003-07-01 20:11 ` James Bottomley
2003-07-01 20:03 ` James Bottomley
2003-07-01 23:01 ` Grant Grundler
2003-07-02 15:52 ` James Bottomley [this message]
2003-07-01 22:51 ` David S. Miller
2003-07-01 23:57 ` [RFC] block layer support for DMA IOMMU bypass mode II Andi Kleen
2003-07-02 0:03 ` David S. Miller
2003-07-02 0:22 ` Andi Kleen
2003-07-02 0:21 ` David S. Miller
2003-07-02 16:53 ` Grant Grundler
2003-07-02 17:19 ` Andi Kleen
2003-07-02 16:55 ` Grant Grundler
2003-07-02 17:20 ` Andi Kleen
2003-07-02 17:37 ` Grant Grundler
2003-07-02 21:16 ` Alan Cox
2003-07-02 23:56 ` Andi Kleen
2003-07-03 20:26 ` Alan Cox
2003-07-03 21:24 ` Andi Kleen
2003-07-03 22:19 ` Grant Grundler
2003-07-08 2:14 ` David S. Miller
2003-07-08 19:34 ` Andi Kleen
2003-07-08 19:47 ` Jeff Garzik
2003-07-08 20:10 ` Andi Kleen
2003-07-08 20:11 ` Grant Grundler
2003-07-08 22:04 ` David S. Miller
2003-07-08 22:25 ` Grant Grundler
2003-07-08 22:23 ` David S. Miller
2003-07-09 18:55 ` Andi Kleen
2003-07-23 11:40 ` Grant Grundler
2003-07-28 11:15 ` Andi Kleen
2003-07-28 14:59 ` Grant Grundler
2003-07-30 2:31 ` Grant Grundler
2003-08-01 21:51 ` Cliff White
2003-08-01 23:18 ` reaim now available as osdl-aim-7 - " Cliff White
2003-07-30 4:42 ` Grant Grundler
2003-07-30 4:51 ` David S. Miller
2003-07-30 13:06 ` Grant Grundler
2003-07-30 16:02 ` Grant Grundler
2003-07-30 16:36 ` Andi Kleen
2003-07-30 17:18 ` James Bottomley
2003-07-30 14:20 ` James Bottomley
2003-07-23 13:20 ` Grant Grundler
2003-07-23 15:30 ` Jens Axboe
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