From 524dabe1c68e0bca25ce7b108099e5d89472a101 Mon Sep 17 00:00:00 2001 From: Alexander Graf Date: Mon, 16 Jan 2017 12:46:33 +0100 Subject: arm64: Fix swiotlb fallback allocation Commit b67a8b29df introduced logic to skip swiotlb allocation when all memory is DMA accessible anyway. While this is a great idea, __dma_alloc still calls swiotlb code unconditionally to allocate memory when there is no CMA memory available. The swiotlb code is called to ensure that we at least try get_free_pages(). Without initialization, swiotlb allocation code tries to access io_tlb_list which is NULL. That results in a stack trace like this: Unable to handle kernel NULL pointer dereference at virtual address 00000000 [...] [] swiotlb_tbl_map_single+0xd0/0x2b0 [] swiotlb_alloc_coherent+0x10c/0x198 [] __dma_alloc+0x68/0x1a8 [] drm_gem_cma_create+0x98/0x108 [drm] [] drm_fbdev_cma_create_with_funcs+0xbc/0x368 [drm_kms_helper] [] drm_fbdev_cma_create+0x2c/0x40 [drm_kms_helper] [] drm_fb_helper_initial_config+0x238/0x410 [drm_kms_helper] [] drm_fbdev_cma_init_with_funcs+0x98/0x160 [drm_kms_helper] [] drm_fbdev_cma_init+0x40/0x58 [drm_kms_helper] [] vc4_kms_load+0x90/0xf0 [vc4] [] vc4_drm_bind+0xec/0x168 [vc4] [...] Thankfully swiotlb code just learned how to not do allocations with the FORCE_NO option. This patch configures the swiotlb code to use that if we decide not to initialize the swiotlb framework. Fixes: b67a8b29df ("arm64: mm: only initialize swiotlb when necessary") Signed-off-by: Alexander Graf CC: Jisheng Zhang CC: Geert Uytterhoeven CC: Konrad Rzeszutek Wilk Signed-off-by: Catalin Marinas --- arch/arm64/mm/init.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 716d1226ba69..380ebe705093 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -404,6 +404,8 @@ void __init mem_init(void) if (swiotlb_force == SWIOTLB_FORCE || max_pfn > (arm64_dma_phys_limit >> PAGE_SHIFT)) swiotlb_init(1); + else + swiotlb_force = SWIOTLB_NO_FORCE; set_max_mapnr(pfn_to_page(max_pfn) - mem_map); -- cgit v1.2.3