On Sat, Oct 02, 2021 at 01:24:54AM +1300, Barry Song wrote: > I assume KVA mode can avoid this iotlb flush as the device is using > the page table of the kernel and sharing the whole kernel space. But > will users be glad to accept this mode?
You can avoid the lock be identity mapping the physical address space of the kernel and maping map/unmap a NOP. KVA is just a different way to achive this identity map with slightly different security properties than the normal way, but it doesn't reach to the same security level as proper map/unmap. I'm not sure anyone who cares about DMA security would see value in the slight difference between KVA and a normal identity map. > which have been mapped in the current dma-map/unmap with IOMMU backend. > some drivers are using bouncing buffer to overcome the performance loss of > dma_map/unmap as copying is faster than unmapping: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=907676b130711fd1f It is pretty unforuntate that drivers are hard coding behaviors based on assumptions of what the portable API is doing under the covers. Jason _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
