On Tue, Jun 09, 2020 at 10:05:26AM +0200, Takashi Iwai wrote: > > >From the disassembly it seems like a vmalloc allocation is NULL, which > > seems really weird as this patch shouldn't make a difference for them, > > and I also only see a single places that allocates the field, and that > > checks for an allocation failure. But the sound code is a little > > hard to unwind sometimes. > > It's not clear which sound device being affected, but if it's > HD-audio on x86, runtime->dma_area points to a vmapped buffer from > SG-pages allocated by dma_alloc_coherent(). > > OTOH, if it's a USB-audio, runtime->dma_area is a buffer by > vmalloc().
Err, you can't just vmap a buffer returned from dma_alloc_coherent, dma_alloc_coherent returns values are opaque and can't be used for virt_to_page. Whatever that code did has already been broken per the DMA API contract and on many architectures and just happend to work on x86 by accident.
