On Mon, Dec 09, 2019 at 04:43:17PM +1100, Michael Ellerman wrote: > Mike Rapoport <[email protected]> writes: > > From: Mike Rapoport <[email protected]> > > > > Some powerpc platforms (e.g. 85xx) limit DMA-able memory way below 4G. If a > > system has more physical memory than this limit, the swiotlb buffer is not > > addressable because it is allocated from memblock using top-down mode. > > > > Force memblock to bottom-up mode before calling swiotlb_init() to ensure > > that the swiotlb buffer is DMA-able. > > > > Link: > > https://lkml.kernel.org/r/[email protected] > > This wasn't bisected, but I thought it was a regression. Do we know what > commit caused it? > > Was it 25078dc1f74b ("powerpc: use mm zones more sensibly") ?
swiotlb buffer is initialized before zones are actually used, so probably not :) > Or was that a red herring? > > cheers > > > Reported-by: Christian Zigotzky <[email protected]> > > Signed-off-by: Mike Rapoport <[email protected]> > > Cc: Benjamin Herrenschmidt <[email protected]> > > Cc: Christoph Hellwig <[email protected]> > > Cc: Darren Stevens <[email protected]> > > Cc: mad skateman <[email protected]> > > Cc: Michael Ellerman <[email protected]> > > Cc: Nicolas Saenz Julienne <[email protected]> > > Cc: Paul Mackerras <[email protected]> > > Cc: Robin Murphy <[email protected]> > > Cc: Rob Herring <[email protected]> > > --- > > arch/powerpc/mm/mem.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c > > index be941d382c8d..14c2c53e3f9e 100644 > > --- a/arch/powerpc/mm/mem.c > > +++ b/arch/powerpc/mm/mem.c > > @@ -260,6 +260,14 @@ void __init mem_init(void) > > BUILD_BUG_ON(MMU_PAGE_COUNT > 16); > > > > #ifdef CONFIG_SWIOTLB > > + /* > > + * Some platforms (e.g. 85xx) limit DMA-able memory way below > > + * 4G. We force memblock to bottom-up mode to ensure that the > > + * memory allocated in swiotlb_init() is DMA-able. > > + * As it's the last memblock allocation, no need to reset it > > + * back to to-down. > > + */ > > + memblock_set_bottom_up(true); > > swiotlb_init(0); > > #endif > > > > -- > > 2.24.0 -- Sincerely yours, Mike.
