On Thu, Oct 15, 2020 at 05:33:34PM +0200, Daniel Vetter wrote: > On Thu, Oct 15, 2020 at 07:55:32AM +0100, Christoph Hellwig wrote: > > On Tue, Oct 13, 2020 at 02:42:38PM +0100, Robin Murphy wrote: > > > I still think this situation would be best handled with a variant of > > > dma_ops_bypass that also guarantees to bypass SWIOTLB, and can be set > > > automatically when attaching to an unmanaged IOMMU domain. > > > > dma_ops_bypass should mostly do the right thing as-is. swiotlb bouncing > > is triggered of two things: > > > > 1) the dma_mask. This is under control of the driver, and obviously > > if it is too small for a legit reason we can't just proceed > > Somewhat related, but is there a way to tell the dma-api to fail instead > of falling back to swiotlb? In many case for gpu drivers it's much better > if we fall back to dma_alloc_coherent and manage the copying ourselves > instead of abstracting this away in the dma-api. Currently that's "solved" > rather pessimistically by always allocating from dma_alloc_coherent if > swiotlb could be in the picture (at least for ttm based drivers, i915 just > falls over). Is this for the alloc_pages plus manually map logic in various drivers? They should switch to the new dma_alloc_pages API that I'll send to Linus for 5.10 soon.
