Messages in this thread | | | Date | Tue, 24 Apr 2007 14:47:33 -0700 (PDT) | Subject | Re: [Intel IOMMU][patch 8/8] Preserve some Virtual Address when devices cannot address entire range. | From | David Miller <> |
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From: Roland Dreier <rdreier@cisco.com> Date: Tue, 24 Apr 2007 14:32:42 -0700
> > My suggestion would be to allocate top-down in the 32-bit IOMMU space. > > I think that's good for normal things, but it's not unreasonable to > want to map > 4 GB of memory at once for an Infiniband device.
That's what the DAC interfaces were for, but people wanted to remoe that since no in-tree users existed.
Devices like that want to essentially map the entire address space, via pass-thru, not IOMMU mappings.
Clustering cards, such as those made by Dolphin, are another example.
I realize that this doesn't work when we absolutely must use an IOMMU such as for virtualization which is the whole impetus of the Intel IOMMU. :-)
> So maybe we would want some heuristics about the size of the mapping > being requested or the amount of 32-bit space left to decide whether a > mapping should be below 4 GB.
Perhaps, but as I said heuristics might not be enough here. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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