Messages in this thread | | | Subject | Re: PATCH: Further aacraid work | From | Benjamin Herrenschmidt <> | Date | Fri, 18 Jun 2004 10:17:21 -0500 |
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> The AMD64 IOMMU could do it too (and the code to do it exists in > 2.6). But the problem is that the current IO layer doesn't provide a > sufficient fallback path when this fails. You have to promise in > advance that you can merge and then later it's too late to change your > mind without signalling an IO error.
Well, the way I do it on ppc64 works with failure cases too. The IO layer is given my phusical limitations, that is it provides me with an SG list that will always fit. If I can do merging, great, that will improve, but I don't enforce merging.
You could do exactly the same.
The problem I agree is that this forces the IO layer to give you small enough requests, it would be nice to have a "try big and retry smaller" path but that require invasive changes.
> I had a chat with James about this at last year's OLS. The Consensus > was iirc that it needs driver interface changes at least.
Ben.
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