From a984fda6b2c24dbf1ca21924f99c8f9418f5765e Mon Sep 17 00:00:00 2001 From: Dave Stevenson Date: Wed, 22 Nov 2023 19:17:44 +0000 Subject: [PATCH] drm: vc4: Block swiotlb bounce buffers being imported as dmabuf The dmabuf import already checks that the backing buffer is contiguous and rejects it if it isn't. vc4 also requires that the buffer is in the bottom 1GB of RAM, and this is all correctly defined via dma-ranges. However the kernel silently uses swiotlb to bounce dma buffers around if they are in the wrong region. This relies on dma sync functions to be called in order to copy the data to/from the bounce buffer. DRM is based on all memory allocations being coherent with the GPU so that any updates to a framebuffer will be acted on without the need for any additional update. This is fairly fundamentally incompatible with needing to call dma_sync_ to handle the bounce buffer copies, and therefore we have to detect and reject mappings that use bounce buffers. Signed-off-by: Dave Stevenson --- drivers/gpu/drm/vc4/vc4_drv.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) --- a/drivers/gpu/drm/vc4/vc4_drv.c +++ b/drivers/gpu/drm/vc4/vc4_drv.c @@ -29,6 +29,7 @@ #include #include #include +#include #include #include @@ -175,6 +176,19 @@ static void vc4_close(struct drm_device kfree(vc4file); } +struct drm_gem_object * +vc4_prime_import_sg_table(struct drm_device *dev, + struct dma_buf_attachment *attach, + struct sg_table *sgt) +{ + phys_addr_t phys = dma_to_phys(dev->dev, sg_dma_address(sgt->sgl)); + + if (is_swiotlb_buffer(dev->dev, phys)) + return ERR_PTR(-EINVAL); + + return drm_gem_dma_prime_import_sg_table(dev, attach, sgt); +} + DEFINE_DRM_GEM_FOPS(vc4_drm_fops); static const struct drm_ioctl_desc vc4_drm_ioctls[] = { @@ -211,7 +225,11 @@ const struct drm_driver vc4_drm_driver = .gem_create_object = vc4_create_object, - DRM_GEM_DMA_DRIVER_OPS_WITH_DUMB_CREATE(vc4_bo_dumb_create), + .dumb_create = vc4_bo_dumb_create, + .prime_handle_to_fd = drm_gem_prime_handle_to_fd, + .prime_fd_to_handle = drm_gem_prime_fd_to_handle, + .gem_prime_import_sg_table = vc4_prime_import_sg_table, + .gem_prime_mmap = drm_gem_prime_mmap, .ioctls = vc4_drm_ioctls, .num_ioctls = ARRAY_SIZE(vc4_drm_ioctls), @@ -234,7 +252,11 @@ const struct drm_driver vc5_drm_driver = .debugfs_init = vc4_debugfs_init, #endif - DRM_GEM_DMA_DRIVER_OPS_WITH_DUMB_CREATE(vc5_dumb_create), + .dumb_create = vc5_dumb_create, + .prime_handle_to_fd = drm_gem_prime_handle_to_fd, + .prime_fd_to_handle = drm_gem_prime_fd_to_handle, + .gem_prime_import_sg_table = vc4_prime_import_sg_table, + .gem_prime_mmap = drm_gem_prime_mmap, .fops = &vc4_drm_fops,