Messages in this thread | | | Subject | Re: [PATCH] dma-pool: Do not allocate pool memory from CMA | From | Nicolas Saenz Julienne <> | Date | Mon, 27 Jul 2020 19:56:56 +0200 |
| |
Hi Christoph, thanks for having a look at this!
On Fri, 2020-07-24 at 15:41 +0200, Christoph Hellwig wrote: > Yes, the iommu is an interesting case, and the current code is > wrong for that.
Care to expand on this? I do get that checking dma_coherent_ok() on memory that'll later on be mapped into an iommu is kind of silly, although I think harmless in Amir's specific case, since devices have wide enough dma-ranges. Is there more to it?
> Can you try the patch below? It contains a modified version of Nicolas' > patch to try CMA again for the expansion and a new (for now hackish) way to > not apply the addressability check for dma-iommu allocations. > > diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c > index 6bc74a2d51273e..ec5e525d2b9309 100644 > --- a/kernel/dma/pool.c > +++ b/kernel/dma/pool.c > @@ -3,7 +3,9 @@ > * Copyright (C) 2012 ARM Ltd. > * Copyright (C) 2020 Google LLC > */ > +#include <linux/cma.h> > #include <linux/debugfs.h> > +#include <linux/dma-contiguous.h> > #include <linux/dma-direct.h> > #include <linux/dma-noncoherent.h> > #include <linux/init.h> > @@ -55,6 +57,31 @@ static void dma_atomic_pool_size_add(gfp_t gfp, size_t > size) > pool_size_kernel += size; > } > > +static bool cma_in_zone(gfp_t gfp) > +{ > + phys_addr_t end; > + unsigned long size; > + struct cma *cma; > + > + cma = dev_get_cma_area(NULL); > + if (!cma) > + return false; > + > + size = cma_get_size(cma); > + if (!size) > + return false; > + end = cma_get_base(cma) - memblock_start_of_DRAM() + size - 1; > + > + /* CMA can't cross zone boundaries, see cma_activate_area() */ > + if (IS_ENABLED(CONFIG_ZONE_DMA) && (gfp & GFP_DMA) && > + end <= DMA_BIT_MASK(zone_dma_bits)) > + return true; > + if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp & GFP_DMA32) && > + end <= DMA_BIT_MASK(32)) > + return true; > + return true;
IIUC this will always return true given a CMA is present. Which reverts to the previous behaviour (previous as in breaking some rpi4 setups), isn't it?
Regards, Nicolas
[unhandled content-type:application/pgp-signature] | |