On Fri, 2017-10-06 at 15:35 -0700, Dan Williams wrote: > Add a helper to determine if the dma mappings set up for a given device > are backed by an iommu. In particular, this lets code paths know that a > dma_unmap operation will revoke access to memory if the device can not > otherwise be quiesced. The need for this knowledge is driven by a need > to make RDMA transfers to DAX mappings safe. If the DAX file's block map > changes we need to be to reliably stop accesses to blocks that have been > freed or re-assigned to a new file. "a dma_unmap operation revoke access to memory"... but it's OK that the next *map* will give the same DMA address to someone else, right?
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