From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:45414 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752393AbdAXIEQ (ORCPT ); Tue, 24 Jan 2017 03:04:16 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexander Graf , Jisheng Zhang , Geert Uytterhoeven , Konrad Rzeszutek Wilk , Catalin Marinas Subject: [PATCH 4.9 106/130] arm64: Fix swiotlb fallback allocation Date: Tue, 24 Jan 2017 08:55:46 +0100 Message-Id: <20170124075539.261689194@linuxfoundation.org> In-Reply-To: <20170124075534.905042535@linuxfoundation.org> References: <20170124075534.905042535@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alexander Graf commit 524dabe1c68e0bca25ce7b108099e5d89472a101 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- arch/arm64/mm/init.c | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -403,6 +403,8 @@ void __init mem_init(void) { if (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);