On Fri, Feb 01, 2019 at 03:15:59PM -0800, Darren Hart wrote: > On Tue, Jan 29, 2019 at 08:34:09AM +0100, Christoph Hellwig wrote: > > For some odd reason dell_rbu actually seems to want the physical and > > not a bus address for the allocated buffer. Lets assume that actually > > is correct given that it is BIOS-related and that is a good source > > of insanity. In that case we should not use dma_alloc_coherent with > > a NULL device to allocate memory, but use GFP_DMA32 to stay under > > the 32-bit BIOS limit. > > + Mario re bios related physical address - is Christoph's assumption > correct? > > Christoph, did you observe a failure? If so, we should probably also > tag for stable. No, I've been auditing for DMA API (ab-)users that don't pass a struct device. Generally the fix was to just pass a struct device that is easily available. But dell_rbu doesn't actually seem to be a "device" in the traditional sense, and the way it uses the DMA API is really, really odd - it first does a virt_to_phys on memory allocated from the page allocator (so works with physical addresses in that case) and the retries with a dma_alloc_coherent with a NULL argument, which in no way is guaranteed to you give you something else, although for the current x86 implementation will give you the equivalent of a GFP_DMA32 page allocator allocation plus virt_to_phys.
