Re: [PATCH v1 07/15] io_uring: Allocate zctap device buffers and dma map them.

Christoph Hellwig
2022-11-16T08:15:57Z

> + dma_unmap_page_attrs(device, buf->dma, PAGE_SIZE,
> + DMA_BIDIRECTIONAL,
> + DMA_ATTR_SKIP_CPU_SYNC);

> + addr = dma_map_page_attrs(device, page, 0, PAGE_SIZE,
> + DMA_BIDIRECTIONAL,
> + DMA_ATTR_SKIP_CPU_SYNC);

You can't just magically skip cpu syncs. The flag is only valid
for mappings of already mapped memory when following a very careful
protocol. I can't see any indications of that beeing true here,
but maybe I'm just missing something.