On Thu, Dec 13, 2018 at 07:45:57PM +0000, Lendacky, Thomas wrote: > So I think this needs to be __phys_to_dma() here. I only recently got a > system that had a device where the driver only supported 32-bit DMA and > found that when SME is active this returns 0 and causes the driver to fail > to initialize. This is because the SME encryption bit (bit 47) is part of > the check when using phys_to_dma(). During actual DMA when SME is active, > bounce buffers will be used for anything that can't meet the 48-bit > requirement. But for this test, using __phys_to_dma() should give the > desired results, right? > > If you agree with this, I'll submit a patch to make the change. I missed > this in 4.19, so I'll need to submit something to stable, too. The only > issue there is the 4.20 fix won't apply cleanly to 4.19.
Yes, please send a patch. Please make sure it includes a code comment that explains why the __-prefixed version is used.