On Tue, Jul 14, 2020 at 7:01 PM Christoph Hellwig <hch@xxxxxx> wrote: > > On Mon, Jul 13, 2020 at 12:55:43PM +0100, Robin Murphy wrote: > > On 2020-07-13 10:12, Claire Chang wrote: > >> The bounced DMA ops provide an implementation of DMA ops that bounce > >> streaming DMA in and out of a specially allocated region. Only the > >> operations relevant to streaming DMA are supported. > > > > I think there are too many implicit assumptions here - apparently that > > coherent allocations will always be intercepted by > > dma_*_from_dev_coherent(), and that calling into dma-direct won't actually > > bounce things a second time beyond where you thought they were going, > > manage coherency for a different address, and make it all go subtly wrong. > > Consider "swiotlb=force", for instance... > > > > Again, plumbing this straight into dma-direct so that SWIOTLB can simply > > target a different buffer and always bounce regardless of masks would seem > > a far better option. > > I haven't really had time to read through the details, but I agree that > any bouncing scheme should reuse the swiotlb code and not invent a > parallel infrastructure. Thanks for the feedback. I'll try to reuse SWIOTLB.
