Merge branch 'dma-api/debug' of git://git.kernel.org/pub/scm/linux/ke…

…rnel/git/joro/linux-2.6-iommu into core/iommu

Documentation/DMA-API.txt

@@ -609,3 +609,109 @@ size is the size (and should be a page-sized multiple).
 The return value will be either a pointer to the processor virtual
 address of the memory, or an error (via PTR_ERR()) if any part of the
 region is occupied.
+
+Part III - Debug drivers use of the DMA-API
+-------------------------------------------
+
+The DMA-API as described above as some constraints. DMA addresses must be
+released with the corresponding function with the same size for example. With
+the advent of hardware IOMMUs it becomes more and more important that drivers
+do not violate those constraints. In the worst case such a violation can
+result in data corruption up to destroyed filesystems.
+
+To debug drivers and find bugs in the usage of the DMA-API checking code can
+be compiled into the kernel which will tell the developer about those
+violations. If your architecture supports it you can select the "Enable
+debugging of DMA-API usage" option in your kernel configuration. Enabling this
+option has a performance impact. Do not enable it in production kernels.
+
+If you boot the resulting kernel will contain code which does some bookkeeping
+about what DMA memory was allocated for which device. If this code detects an
+error it prints a warning message with some details into your kernel log. An
+example warning message may look like this:
+
+------------[ cut here ]------------
+WARNING: at /data2/repos/linux-2.6-iommu/lib/dma-debug.c:448
+	check_unmap+0x203/0x490()
+Hardware name:
+forcedeth 0000:00:08.0: DMA-API: device driver frees DMA memory with wrong
+	function [device address=0x00000000640444be] [size=66 bytes] [mapped as
+single] [unmapped as page]
+Modules linked in: nfsd exportfs bridge stp llc r8169
+Pid: 0, comm: swapper Tainted: G        W  2.6.28-dmatest-09289-g8bb99c0 #1
+Call Trace:
+ <IRQ>  [<ffffffff80240b22>] warn_slowpath+0xf2/0x130
+ [<ffffffff80647b70>] _spin_unlock+0x10/0x30
+ [<ffffffff80537e75>] usb_hcd_link_urb_to_ep+0x75/0xc0
+ [<ffffffff80647c22>] _spin_unlock_irqrestore+0x12/0x40
+ [<ffffffff8055347f>] ohci_urb_enqueue+0x19f/0x7c0
+ [<ffffffff80252f96>] queue_work+0x56/0x60
+ [<ffffffff80237e10>] enqueue_task_fair+0x20/0x50
+ [<ffffffff80539279>] usb_hcd_submit_urb+0x379/0xbc0
+ [<ffffffff803b78c3>] cpumask_next_and+0x23/0x40
+ [<ffffffff80235177>] find_busiest_group+0x207/0x8a0
+ [<ffffffff8064784f>] _spin_lock_irqsave+0x1f/0x50
+ [<ffffffff803c7ea3>] check_unmap+0x203/0x490
+ [<ffffffff803c8259>] debug_dma_unmap_page+0x49/0x50
+ [<ffffffff80485f26>] nv_tx_done_optimized+0xc6/0x2c0
+ [<ffffffff80486c13>] nv_nic_irq_optimized+0x73/0x2b0
+ [<ffffffff8026df84>] handle_IRQ_event+0x34/0x70
+ [<ffffffff8026ffe9>] handle_edge_irq+0xc9/0x150
+ [<ffffffff8020e3ab>] do_IRQ+0xcb/0x1c0
+ [<ffffffff8020c093>] ret_from_intr+0x0/0xa
+ <EOI> <4>---[ end trace f6435a98e2a38c0e ]---
+
+The driver developer can find the driver and the device including a stacktrace
+of the DMA-API call which caused this warning.
+
+Per default only the first error will result in a warning message. All other
+errors will only silently counted. This limitation exist to prevent the code
+from flooding your kernel log. To support debugging a device driver this can
+be disabled via debugfs. See the debugfs interface documentation below for
+details.
+
+The debugfs directory for the DMA-API debugging code is called dma-api/. In
+this directory the following files can currently be found:
+
+	dma-api/all_errors	This file contains a numeric value. If this
+				value is not equal to zero the debugging code
+				will print a warning for every error it finds
+				into the kernel log. Be carefull with this
+				option. It can easily flood your logs.
+
+	dma-api/disabled	This read-only file contains the character 'Y'
+				if the debugging code is disabled. This can
+				happen when it runs out of memory or if it was
+				disabled at boot time
+
+	dma-api/error_count	This file is read-only and shows the total
+				numbers of errors found.
+
+	dma-api/num_errors	The number in this file shows how many
+				warnings will be printed to the kernel log
+				before it stops. This number is initialized to
+				one at system boot and be set by writing into
+				this file
+
+	dma-api/min_free_entries
+				This read-only file can be read to get the
+				minimum number of free dma_debug_entries the
+				allocator has ever seen. If this value goes
+				down to zero the code will disable itself
+				because it is not longer reliable.
+
+	dma-api/num_free_entries
+				The current number of free dma_debug_entries
+				in the allocator.
+
+If you have this code compiled into your kernel it will be enabled by default.
+If you want to boot without the bookkeeping anyway you can provide
+'dma_debug=off' as a boot parameter. This will disable DMA-API debugging.
+Notice that you can not enable it again at runtime. You have to reboot to do
+so.
+
+When the code disables itself at runtime this is most likely because it ran
+out of dma_debug_entries. These entries are preallocated at boot. The number
+of preallocated entries is defined per architecture. If it is too low for you
+boot with 'dma_debug_entries=<your_desired_number>' to overwrite the
+architectural default.

Documentation/kernel-parameters.txt

@@ -491,6 +491,16 @@ and is between 256 and 4096 characters. It is defined in the file
 			Range: 0 - 8192
 			Default: 64
 
+	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support
+			this option disables the debugging code at boot.
+
+	dma_debug_entries=<number>
+			This option allows to tune the number of preallocated
+			entries for DMA-API debugging code. One entry is
+			required per DMA-API allocation. Use this if the
+			DMA-API debugging code disables itself because the
+			architectural default is too low.
+
 	hpet=		[X86-32,HPET] option to control HPET usage
 			Format: { enable (default) | disable | force }
 			disable: disable HPET and use PIT instead

arch/Kconfig

@@ -106,3 +106,5 @@ config HAVE_CLK
 	  The <linux/clk.h> calls support software clock gating and
 	  thus are a key power management tool on many systems.
 
+config HAVE_DMA_API_DEBUG
+	bool

arch/x86/Kconfig

@@ -40,6 +40,7 @@ config X86
 	select HAVE_GENERIC_DMA_COHERENT if X86_32
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS
 	select USER_STACKTRACE_SUPPORT
+	select HAVE_DMA_API_DEBUG
 
 config ARCH_DEFCONFIG
 	string

arch/x86/include/asm/dma-mapping.h

@@ -7,6 +7,7 @@
  */
 
 #include <linux/scatterlist.h>
+#include <linux/dma-debug.h>
 #include <linux/dma-attrs.h>
 #include <asm/io.h>
 #include <asm/swiotlb.h>
@@ -56,11 +57,16 @@ dma_map_single(struct device *hwdev, void *ptr, size_t size,
 	       enum dma_data_direction dir)
 {
 	struct dma_map_ops *ops = get_dma_ops(hwdev);
+	dma_addr_t addr;
 
 	BUG_ON(!valid_dma_direction(dir));
-	return ops->map_page(hwdev, virt_to_page(ptr),
+	addr = ops->map_page(hwdev, virt_to_page(ptr),
 			     (unsigned long)ptr & ~PAGE_MASK, size,
 			     dir, NULL);
+	debug_dma_map_page(hwdev, virt_to_page(ptr),
+			   (unsigned long)ptr & ~PAGE_MASK, size,
+			   dir, addr, true);
+	return addr;
 }
 
 static inline void
@@ -72,16 +78,21 @@ dma_unmap_single(struct device *dev, dma_addr_t addr, size_t size,
 	BUG_ON(!valid_dma_direction(dir));
 	if (ops->unmap_page)
 		ops->unmap_page(dev, addr, size, dir, NULL);
+	debug_dma_unmap_page(dev, addr, size, dir, true);
 }
 
 static inline int
 dma_map_sg(struct device *hwdev, struct scatterlist *sg,
 	   int nents, enum dma_data_direction dir)
 {
 	struct dma_map_ops *ops = get_dma_ops(hwdev);
+	int ents;
 
 	BUG_ON(!valid_dma_direction(dir));
-	return ops->map_sg(hwdev, sg, nents, dir, NULL);
+	ents = ops->map_sg(hwdev, sg, nents, dir, NULL);
+	debug_dma_map_sg(hwdev, sg, nents, ents, dir);
+
+	return ents;
 }
 
 static inline void
@@ -91,6 +102,7 @@ dma_unmap_sg(struct device *hwdev, struct scatterlist *sg, int nents,
 	struct dma_map_ops *ops = get_dma_ops(hwdev);
 
 	BUG_ON(!valid_dma_direction(dir));
+	debug_dma_unmap_sg(hwdev, sg, nents, dir);
 	if (ops->unmap_sg)
 		ops->unmap_sg(hwdev, sg, nents, dir, NULL);
 }
@@ -104,6 +116,7 @@ dma_sync_single_for_cpu(struct device *hwdev, dma_addr_t dma_handle,
 	BUG_ON(!valid_dma_direction(dir));
 	if (ops->sync_single_for_cpu)
 		ops->sync_single_for_cpu(hwdev, dma_handle, size, dir);
+	debug_dma_sync_single_for_cpu(hwdev, dma_handle, size, dir);
 	flush_write_buffers();
 }
 
@@ -116,6 +129,7 @@ dma_sync_single_for_device(struct device *hwdev, dma_addr_t dma_handle,
 	BUG_ON(!valid_dma_direction(dir));
 	if (ops->sync_single_for_device)
 		ops->sync_single_for_device(hwdev, dma_handle, size, dir);
+	debug_dma_sync_single_for_device(hwdev, dma_handle, size, dir);
 	flush_write_buffers();
 }
 
@@ -130,6 +144,8 @@ dma_sync_single_range_for_cpu(struct device *hwdev, dma_addr_t dma_handle,
 	if (ops->sync_single_range_for_cpu)
 		ops->sync_single_range_for_cpu(hwdev, dma_handle, offset,
 					       size, dir);
+	debug_dma_sync_single_range_for_cpu(hwdev, dma_handle,
+					    offset, size, dir);
 	flush_write_buffers();
 }
 
@@ -144,6 +160,8 @@ dma_sync_single_range_for_device(struct device *hwdev, dma_addr_t dma_handle,
 	if (ops->sync_single_range_for_device)
 		ops->sync_single_range_for_device(hwdev, dma_handle,
 						  offset, size, dir);
+	debug_dma_sync_single_range_for_device(hwdev, dma_handle,
+					       offset, size, dir);
 	flush_write_buffers();
 }
 
@@ -156,6 +174,7 @@ dma_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
 	BUG_ON(!valid_dma_direction(dir));
 	if (ops->sync_sg_for_cpu)
 		ops->sync_sg_for_cpu(hwdev, sg, nelems, dir);
+	debug_dma_sync_sg_for_cpu(hwdev, sg, nelems, dir);
 	flush_write_buffers();
 }
 
@@ -168,6 +187,7 @@ dma_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
 	BUG_ON(!valid_dma_direction(dir));
 	if (ops->sync_sg_for_device)
 		ops->sync_sg_for_device(hwdev, sg, nelems, dir);
+	debug_dma_sync_sg_for_device(hwdev, sg, nelems, dir);
 
 	flush_write_buffers();
 }
@@ -177,15 +197,24 @@ static inline dma_addr_t dma_map_page(struct device *dev, struct page *page,
 				      enum dma_data_direction dir)
 {
 	struct dma_map_ops *ops = get_dma_ops(dev);
+	dma_addr_t addr;
 
 	BUG_ON(!valid_dma_direction(dir));
-	return ops->map_page(dev, page, offset, size, dir, NULL);
+	addr = ops->map_page(dev, page, offset, size, dir, NULL);
+	debug_dma_map_page(dev, page, offset, size, dir, addr, false);
+
+	return addr;
 }
 
 static inline void dma_unmap_page(struct device *dev, dma_addr_t addr,
 				  size_t size, enum dma_data_direction dir)
 {
-	dma_unmap_single(dev, addr, size, dir);
+	struct dma_map_ops *ops = get_dma_ops(dev);
+
+	BUG_ON(!valid_dma_direction(dir));
+	if (ops->unmap_page)
+		ops->unmap_page(dev, addr, size, dir, NULL);
+	debug_dma_unmap_page(dev, addr, size, dir, false);
 }
 
 static inline void
@@ -250,8 +279,11 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	if (!ops->alloc_coherent)
 		return NULL;
 
-	return ops->alloc_coherent(dev, size, dma_handle,
-				   dma_alloc_coherent_gfp_flags(dev, gfp));
+	memory = ops->alloc_coherent(dev, size, dma_handle,
+				     dma_alloc_coherent_gfp_flags(dev, gfp));
+	debug_dma_alloc_coherent(dev, size, *dma_handle, memory);
+
+	return memory;
 }
 
 static inline void dma_free_coherent(struct device *dev, size_t size,
@@ -264,6 +296,7 @@ static inline void dma_free_coherent(struct device *dev, size_t size,
 	if (dma_release_from_coherent(dev, get_order(size), vaddr))
 		return;
 
+	debug_dma_free_coherent(dev, size, vaddr, bus);
 	if (ops->free_coherent)
 		ops->free_coherent(dev, size, vaddr, bus);
 }

arch/x86/kernel/pci-dma.c

@@ -1,4 +1,5 @@
 #include <linux/dma-mapping.h>
+#include <linux/dma-debug.h>
 #include <linux/dmar.h>
 #include <linux/bootmem.h>
 #include <linux/pci.h>
@@ -44,6 +45,9 @@ struct device x86_dma_fallback_dev = {
 };
 EXPORT_SYMBOL(x86_dma_fallback_dev);
 
+/* Number of entries preallocated for DMA-API debugging */
+#define PREALLOC_DMA_DEBUG_ENTRIES       32768
+
 int dma_set_mask(struct device *dev, u64 mask)
 {
 	if (!dev->dma_mask || !dma_supported(dev, mask))
@@ -265,6 +269,12 @@ EXPORT_SYMBOL(dma_supported);
 
 static int __init pci_iommu_init(void)
 {
+	dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
+
+#ifdef CONFIG_PCI
+	dma_debug_add_bus(&pci_bus_type);
+#endif
+
 	calgary_iommu_init();
 
 	intel_iommu_init();