Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934764AbcLPN3O (ORCPT ); Fri, 16 Dec 2016 08:29:14 -0500 Received: from albert.telenet-ops.be ([195.130.137.90]:38194 "EHLO albert.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757565AbcLPN3I (ORCPT ); Fri, 16 Dec 2016 08:29:08 -0500 From: Geert Uytterhoeven To: Konrad Rzeszutek Wilk Cc: Jonathan Corbet , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Boris Ostrovsky , David Vrabel , Juergen Gross , Steven Rostedt , linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Geert Uytterhoeven Subject: [PATCH v2 3/3] swiotlb: Add swiotlb=noforce debug option Date: Fri, 16 Dec 2016 14:28:42 +0100 Message-Id: <1481894922-28828-4-git-send-email-geert+renesas@glider.be> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1481894922-28828-1-git-send-email-geert+renesas@glider.be> References: <1481894922-28828-1-git-send-email-geert+renesas@glider.be> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4023 Lines: 115 On architectures like arm64, swiotlb is tied intimately to the core architecture DMA support. In addition, ZONE_DMA cannot be disabled. To aid debugging and catch devices not supporting DMA to memory outside the 32-bit address space, add a kernel command line option "swiotlb=noforce", which disables the use of bounce buffers. If specified, trying to map memory that cannot be used with DMA will fail, and a rate-limited warning will be printed. Note that io_tlb_nslabs is set to 1, which is the minimal supported value. Signed-off-by: Geert Uytterhoeven --- v2: - Change kernel parameter value from "nobounce" to "noforce", - Extend swiotlb_force enum instead of adding swiotlb_nobounce variable (both requested by Konrad Wilk). --- Documentation/admin-guide/kernel-parameters.txt | 3 ++- include/linux/swiotlb.h | 1 + include/trace/events/swiotlb.h | 3 ++- lib/swiotlb.c | 18 ++++++++++++++++-- 4 files changed, 21 insertions(+), 4 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 21e2d88637050b7a..24fb691b2da5f78d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3811,10 +3811,11 @@ it if 0 is given (See Documentation/cgroup-v1/memory.txt) swiotlb= [ARM,IA-64,PPC,MIPS,X86] - Format: { | force } + Format: { | force | noforce } -- Number of I/O TLB slabs force -- force using of bounce buffers even if they wouldn't be automatically used by the kernel + noforce -- Never use bounce buffers (for debugging) switches= [HW,M68k] diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index 71d104e4c8490763..d9c84a9cde3dd7d7 100644 --- a/include/linux/swiotlb.h +++ b/include/linux/swiotlb.h @@ -12,6 +12,7 @@ enum swiotlb_force { SWIOTLB_NORMAL, /* Default - depending on HW DMA mask etc. */ SWIOTLB_FORCE, /* swiotlb=force */ + SWIOTLB_NO_FORCE, /* swiotlb=noforce */ }; extern enum swiotlb_force swiotlb_force; diff --git a/include/trace/events/swiotlb.h b/include/trace/events/swiotlb.h index 5e2e30a7efce0ebd..288c0c54a2b4ace6 100644 --- a/include/trace/events/swiotlb.h +++ b/include/trace/events/swiotlb.h @@ -39,7 +39,8 @@ __entry->size, __print_symbolic(__entry->swiotlb_force, { SWIOTLB_NORMAL, "NORMAL" }, - { SWIOTLB_FORCE, "FORCE" })) + { SWIOTLB_FORCE, "FORCE" }, + { SWIOTLB_NO_FORCE, "NO_FORCE" })) ); #endif /* _TRACE_SWIOTLB_H */ diff --git a/lib/swiotlb.c b/lib/swiotlb.c index a32dce6d5101f408..9def738af4f4e568 100644 --- a/lib/swiotlb.c +++ b/lib/swiotlb.c @@ -106,8 +106,12 @@ } if (*str == ',') ++str; - if (!strcmp(str, "force")) + if (!strcmp(str, "force")) { swiotlb_force = SWIOTLB_FORCE; + } else if (!strcmp(str, "noforce")) { + swiotlb_force = SWIOTLB_NO_FORCE; + io_tlb_nslabs = 1; + } return 0; } @@ -543,8 +547,15 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, map_single(struct device *hwdev, phys_addr_t phys, size_t size, enum dma_data_direction dir, unsigned long attrs) { - dma_addr_t start_dma_addr = phys_to_dma(hwdev, io_tlb_start); + dma_addr_t start_dma_addr; + + if (swiotlb_force == SWIOTLB_NO_FORCE) { + dev_warn_ratelimited(hwdev, "Cannot do DMA to address %pa\n", + &phys); + return SWIOTLB_MAP_ERROR; + } + start_dma_addr = phys_to_dma(hwdev, io_tlb_start); return swiotlb_tbl_map_single(hwdev, start_dma_addr, phys, size, dir, attrs); } @@ -721,6 +732,9 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr, swiotlb_full(struct device *dev, size_t size, enum dma_data_direction dir, int do_panic) { + if (swiotlb_force == SWIOTLB_NO_FORCE) + return; + /* * Ran out of IOMMU space for this operation. This is very bad. * Unfortunately the drivers cannot handle this operation properly. -- 1.9.1