From: James Bottomley <James.Bottomley@steeleye.com>
To: Alex Williamson <alex_williamson@hp.com>
Cc: Grant Grundler <grundler@parisc-linux.org>,
Jens Axboe <axboe@suse.de>,
ak@suse.de, davem@redhat.com, suparna@in.ibm.com,
Linux Kernel <linux-kernel@vger.kernel.org>,
Bjorn Helgaas <bjorn_helgaas@hp.com>
Subject: Re: [RFC] block layer support for DMA IOMMU bypass mode
Date: 01 Jul 2003 15:11:16 -0500 [thread overview]
Message-ID: <1057090278.1775.117.camel@mulgrave> (raw)
In-Reply-To: <3F01E81E.813FCDAC@hp.com>
On Tue, 2003-07-01 at 14:59, Alex Williamson wrote:
> The thing that's got me concerned about this is that it allows
> for sg lists that contains both entries that the block layer
> expects will be mapped into the iommu and ones that it expects
> to bypass. I don't like the implications of parsing through
> sg lists looking for bypass-able and non-bypass-able groupings.
> This seems like a lot more overhead than we have now and the
> complexity of merging partially bypass-able scatterlists seems
> time consuming.
>
> The current ia64 sba_iommu does a quick and dirty sg bypass
> check. If the device can dma to any memory address, the entire
> sg list is bypassed. If not, the entire list is coalesced and
> mapped by the iommu. The idea being that true performance
> devices will have 64bit dma masks and be able to quickly bypass.
> Everything else will at least get the benefit of coalescing
> entries to make more efficient dma. The coalescing is a bit
> simpler since it's the entire list as well. With this proposal,
> we'd have to add a lot of complexity to partially bypass sg
> lists. I don't necessarily see that as a benefit. Thanks,
But if that's all you want, you simply set the BIO_VMERGE_BYPASS_MASK to
the full u64 set bitmask. Then it will only turn off virtual merging
for devices that have a fully set dma_mask, and your simple test will
work.
James
next prev parent reply other threads:[~2003-07-01 19:57 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 [this message]
2003-07-01 20:03 ` James Bottomley
2003-07-01 23:01 ` Grant Grundler
2003-07-02 15:52 ` James Bottomley
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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