Messages in this thread | | | Subject | Re: [PATCH v3 02/10] swiotlb: Factor out slot allocation and free | From | Lu Baolu <> | Date | Mon, 29 Apr 2019 13:10:17 +0800 |
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Hi Christoph,
On 4/26/19 11:04 PM, Christoph Hellwig wrote: > On Thu, Apr 25, 2019 at 10:07:19AM +0800, Lu Baolu wrote: >> This is not VT-d specific. It's just how generic IOMMU works. >> >> Normally, IOMMU works in paging mode. So if a driver issues DMA with >> IOVA 0xAAAA0123, IOMMU can remap it with a physical address 0xBBBB0123. >> But we should never expect IOMMU to remap 0xAAAA0123 with physical >> address of 0xBBBB0000. That's the reason why I said that IOMMU will not >> work there. > > Well, with the iommu it doesn't happen. With swiotlb it obviosuly > can happen, so drivers are fine with it. Why would that suddenly > become an issue when swiotlb is called from the iommu code? >
I would say IOMMU is DMA remapping, not DMA engine. :-)
Best regards, Lu Baolu
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