On Thu, 21 Apr 2022 at 09:20, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > Btw, there is another option: Most real systems already require having > swiotlb to bounce buffer in some cases. We could simply force bounce > buffering in the dma mapping code for too small or not properly aligned > transfers and just decrease the dma alignment. Strongly agree. As I pointed out before, we'd only need to do this for misaligned, non-cache coherent inbound DMA, and we'd only have to worry about performance regressions, not data corruption issues. And given the natural alignment of block I/O, and the fact that network drivers typically allocate and map their own RX buffers (which means they could reasonably be fixed if a performance bottleneck pops up), I think the risk for showstopper performance regressions is likely to be acceptable.
