Re: [PATCH v7 1/5] drm/gpusvm: Use dma-map IOVA alloc, link, and sync API in GPU SVM

[Nathan Chancellor <nathan@kernel.org>]

Hi Matthew,

On Fri, Apr 10, 2026 at 01:59:25PM -0700, Matthew Brost wrote:
> diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
> index 7993e85c0566..365a9c0b522a 100644
> --- a/drivers/gpu/drm/drm_gpusvm.c
> +++ b/drivers/gpu/drm/drm_gpusvm.c
> @@ -1544,13 +1554,33 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
>  				goto err_unmap;
>  			}
>  
> -			addr = dma_map_page(gpusvm->drm->dev,
> -					    page, 0,
> -					    PAGE_SIZE << order,
> -					    dma_dir);
> -			if (dma_mapping_error(gpusvm->drm->dev, addr)) {
> -				err = -EFAULT;
> -				goto err_unmap;
> +			if (!i)
> +				dma_iova_try_alloc(gpusvm->drm->dev, state,
> +						   npages * PAGE_SIZE >=
> +						   HPAGE_PMD_SIZE ?
> +						   HPAGE_PMD_SIZE : 0,
> +						   npages * PAGE_SIZE);

This patch is in -next as commit 37ad039fb367 ("drm/gpusvm: Use dma-map
IOVA alloc, link, and sync API in GPU SVM"), where it breaks the build
for certain platforms such as ARM.

  $ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- mrproper allmodconfig drivers/gpu/drm/drm_gpusvm.o
  In file included from <command-line>:
  drivers/gpu/drm/drm_gpusvm.c: In function 'drm_gpusvm_get_pages':
  include/linux/compiler_types.h:699:45: error: call to '__compiletime_assert_361' declared with attribute error: BUILD_BUG failed
    699 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
        |                                             ^
  include/linux/compiler_types.h:680:25: note: in definition of macro '__compiletime_assert'
    680 |                         prefix ## suffix();                             \
        |                         ^~~~~~
  include/linux/compiler_types.h:699:9: note: in expansion of macro '_compiletime_assert'
    699 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
        |         ^~~~~~~~~~~~~~~~~~~
  include/linux/build_bug.h:40:37: note: in expansion of macro 'compiletime_assert'
     40 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
        |                                     ^~~~~~~~~~~~~~~~~~
  include/linux/build_bug.h:60:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
     60 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
        |                     ^~~~~~~~~~~~~~~~
  include/linux/huge_mm.h:113:28: note: in expansion of macro 'BUILD_BUG'
    113 | #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
        |                            ^~~~~~~~~
  include/linux/huge_mm.h:120:35: note: in expansion of macro 'HPAGE_PMD_SHIFT'
    120 | #define HPAGE_PMD_SIZE  ((1UL) << HPAGE_PMD_SHIFT)
        |                                   ^~~~~~~~~~~~~~~
  drivers/gpu/drm/drm_gpusvm.c:1560:52: note: in expansion of macro 'HPAGE_PMD_SIZE'
   1560 |                                                    HPAGE_PMD_SIZE ?
        |                                                    ^~~~~~~~~~~~~~
  make[7]: *** [scripts/Makefile.build:289: drivers/gpu/drm/drm_gpusvm.o] Error 1
  ...

I think use of HPAGE_PMD_SIZE is expected to be gated by
CONFIG_TRANSPARENT_HUGEPAGE ifdefs?

Cheers,
Nathan