On Tue, Aug 07, 2018 at 12:46:34AM +0300, Michael S. Tsirkin wrote: > Well we have the RFC for that - the switch to using DMA ops unconditionally > isn't > problematic itself IMHO, for now that RFC is blocked > by its perfromance overhead for now but Christoph says > he's trying to remove that for direct mappings, > so we should hopefully be able to get there in X weeks.
The direct calls to dma_direct_ops aren't going to help you with legacy virtio, given that virtio is specified to deal with physical addresses, while dma-direct is not in many cases. It would however help with the case where qemu always sets the platform dma flag, as we'd avoid the indirect calls for that.
