Messages in this thread | | | Date | Thu, 25 May 2006 12:42:36 +0300 | From | Muli Ben-Yehuda <> | Subject | Re: [PATCH 2/4] x86-64: Calgary IOMMU - move valid_dma_direction into the callers |
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On Thu, May 25, 2006 at 12:35:07AM -0400, Jeff Garzik wrote: > Jon Mason wrote: > >>From Andi Kleen's comments on the original Calgary patch, move > >valid_dma_direction into the calling functions. > > > >Signed-off-by: Muli Ben-Yehuda <muli@il.ibm.com> > >Signed-off-by: Jon Mason <jdmason@us.ibm.com> > > Even though BUG_ON() includes unlikely(), this introduces additional > tests in very hot paths.
Are they really very hot? I mean if you're calling the DMA API, you're about to frob the hardware or have already frobbed it - does this check really matter?
> _Why_ do we need this at all?
It was helpful for us during the dma-ops work and Calgary bringup and Andi requested that we move it from Calgary to common code. I think we're fine with dropping it if that's the consensus, but it did catch a few bugs early on and the cost is tiny.
Cheers, Muli -- Muli Ben-Yehuda http://www.mulix.org | http://mulix.livejournal.com/
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