Messages in this thread | | | Date | Tue, 6 Aug 2019 08:43:47 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH 2/3] iommu/vt-d: Apply per-device dma_ops |
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Hi Lu,
I really do like the switch to the per-device dma_map_ops, but:
On Thu, Aug 01, 2019 at 02:01:55PM +0800, Lu Baolu wrote: > Current Intel IOMMU driver sets the system level dma_ops. This > implementation has at least the following drawbacks: 1) each > dma API will go through the IOMMU driver even the devices are > using identity mapped domains; 2) if user requests to use an > identity mapped domain (a.k.a. bypass iommu translation), the > driver might fall back to dma domain blindly if the device is > not able to address all system memory.
This is very clearly a behavioral regression. The intel-iommu driver has always used the iommu mapping to provide decent support for devices that do not have the full 64-bit addressing capability, and changing this will make a lot of existing setups go slower.
I don't think having to use swiotlb for these devices helps anyone.
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