On 19/03/18 15:24, Christoph Hellwig wrote:
On Mon, Mar 19, 2018 at 03:19:04PM +0000, Robin Murphy wrote:As a heads-up, I've just realised there's now a silent (but build-breaking) conflict with the current arm64 queue brewing here, as we've unfortunately had to reintroduce ARCH_HAS_PHYS_TO_DMA as a means of being safe against an ugly architectural corner case - currently commit 1f85b42a691c ("arm64: Revert L1_CACHE_SHIFT back to 6 (64-byte cache line size)") in -next.Please revert that arm64 commit. This condition should be handled in common code as it is not arm specific. And next time please CC the iommu list and dma-mapping maintainers before doing such a change.
There didn't seem enough justification to clutter up core SWIOTLB code with the ability to force bouncing on a per-device basis, but if you think there are real potential users out there then fair enough. For arm64, it's extremely unlikely that anyone will ever build a sufficiently wacky system to actually hit this code path; we really only implemented it for peace of mind per the letter of the architecture.
Robin.
