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Date: Thu, 4 Oct 2012 13:38:29 -0400
From: Konrad Rzeszutek Wilk <konrad@...nel.org>
To: Shuah Khan <shuah.khan@...com>
Cc: konrad.wilk@...cle.com, tglx@...utronix.de, mingo@...hat.com,
hpa@...or.com, rob@...dley.net, akpm@...ux-foundation.org,
stern@...land.harvard.edu, joerg.roedel@....com,
bhelgaas@...gle.com, LKML <linux-kernel@...r.kernel.org>,
linux-doc@...r.kernel.org, devel@...uxdriverproject.org,
x86@...nel.org, shuahkhan@...il.com
Subject: Re: [PATCH v3] dma-debug: New interfaces to debug dma mapping errors
On Wed, Oct 03, 2012 at 08:55:59AM -0600, Shuah Khan wrote:
> A recent dma mapping error analysis effort showed that a large percentage
> of dma_map_single() and dma_map_page() returns are not checked for mapping
> errors.
>
> Reference:
> http://linuxdriverproject.org/mediawiki/index.php/DMA_Mapping_Error_Analysis
>
> Adding support for tracking dma mapping and unmapping errors to help assess
> the following:
>
> When do dma mapping errors get detected?
> How often do these errors occur?
> Why don't we see failures related to missing dma mapping error checks?
> Are they silent failures?
>
> Patch v3: Addresses review and design comments from Patch v2.
> Patch v2: Addressed design issues from Patch v1.
>
> Enhance dma-debug infrastructure to track dma mapping, and unmapping errors.
>
> map_errors: (system wide counter)
> Total number of dma mapping errors returned by the dma mapping interfaces,
> in response to mapping requests from all devices in the system.
> map_errors_not_checked: (system wide counter)
> Total number of dma mapping errors devices failed to check before using
> the returned address.
> unmap_errors: (system wide counter)
> Total number of times devices tried to unmap or free an invalid dma
> address.
> map_err_type: (new field added to dma_debug_entry structure)
> New field to maintain dma mapping error check status. This error type
> is applicable to the dma map page and dma map single entries tracked by
> dma-debug api. This status indicates whether or not a good mapping is
> checked by the device before its use. dma_map_single() and dma_map_page()
> could fail to create a mapping in some cases, and drivers are expected to
> call dma_mapping_error() to check for errors. Please note that this is not
> counter.
>
> Enhancements to dma-debug api are made to add new debugfs interfaces to
> report total dma errors, dma errors that are not checked, and unmap errors
> for the entire system. Please note that these are system wide counters for
> all devices in the system.
>
> The following new dma-debug interface is added:
>
> debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
> Sets dma map error checked status for the dma map entry if one is
> found. Decrements the system wide dma_map_errors_not_checked counter
> that is incremented by debug_dma_map_page() when it checks for
> mapping error before adding it to the dma debug entry table.
>
> New dma-debug internal interface:
> check_mapping_error(struct device *dev, dma_addr_t dma_addr)
> Calling dma_mapping_error() from dma-debug api will result in dma mapping
> check when it shouldn't. This internal routine checks dma mapping error
> without any debug checks.
>
> The following existing dma-debug api are changed to support this feature:
> debug_dma_map_page()
> Increments dma_map_errors and dma_map_errors_not_checked errors totals
> for the system, dma-debug api keeps track of, when dma_addr is invalid.
> This routine now calls internal check_mapping_error() interface to
> avoid doing dma mapping debug checks from dma-debug internal mapping
> error checks.
> check_unmap()
> This is an existing internal routines that checks for various mapping
> errors. Changed to increment system wide dma_unmap_errors, when a
> device requests an invalid address to be unmapped. This routine now
> calls internal check_mapping_error() interface to avoid doing dma
> mapping debug checks from dma-debug internal mapping error checks.
>
> Changed arch/x86/include/asm/dma-mapping.h to call debug_dma_mapping_error()
> to validate these new interfaces on x86_64. Other architectures will be
> changed in a subsequent patch.
>
> Tested: Intel iommu and swiotlb (iommu=soft) on x86-64 with
> CONFIG_DMA_API_DEBUG enabled and disabled.
>
> Signed-off-by: Shuah Khan <shuah.khan@...com>
> ---
> Documentation/DMA-API.txt | 13 ++++
> arch/x86/include/asm/dma-mapping.h | 1 +
> include/linux/dma-debug.h | 7 ++
> lib/dma-debug.c | 128 ++++++++++++++++++++++++++++++++----
> 4 files changed, 136 insertions(+), 13 deletions(-)
>
> diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
> index 66bd97a..886aaf9 100644
> --- a/Documentation/DMA-API.txt
> +++ b/Documentation/DMA-API.txt
> @@ -638,6 +638,19 @@ this directory the following files can currently be found:
> dma-api/error_count This file is read-only and shows the total
> numbers of errors found.
>
> + dma-api/map_errors This file is read-only and shows the total
> + number of dma mapping errors detected.
> +
> + dma-api/map_errors_not_checked
> + This file is read-only and shows the total
> + number of dma mapping errors, device drivers
> + failed to check prior to using the returned
> + address.
> +
> + dma-api/unmap_errors
> + This file is read-only and shows the total
> + number of invalid dma unmapping attempts.
> +
> 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
> diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h
> index f7b4c79..808dae6 100644
> --- a/arch/x86/include/asm/dma-mapping.h
> +++ b/arch/x86/include/asm/dma-mapping.h
> @@ -47,6 +47,7 @@ static inline struct dma_map_ops *get_dma_ops(struct device *dev)
> static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
> {
> struct dma_map_ops *ops = get_dma_ops(dev);
> + debug_dma_mapping_error(dev, dma_addr);
> if (ops->mapping_error)
> return ops->mapping_error(dev, dma_addr);
>
> diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h
> index 171ad8a..fc0e34c 100644
> --- a/include/linux/dma-debug.h
> +++ b/include/linux/dma-debug.h
> @@ -39,6 +39,8 @@ extern void debug_dma_map_page(struct device *dev, struct page *page,
> int direction, dma_addr_t dma_addr,
> bool map_single);
>
> +extern void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
> +
> extern void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
> size_t size, int direction, bool map_single);
>
> @@ -105,6 +107,11 @@ static inline void debug_dma_map_page(struct device *dev, struct page *page,
> {
> }
>
> +static inline void debug_dma_mapping_error(struct device *dev,
> + dma_addr_t dma_addr)
> +{
> +}
> +
> static inline void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
> size_t size, int direction,
> bool map_single)
> diff --git a/lib/dma-debug.c b/lib/dma-debug.c
> index 66ce414..1708a10 100644
> --- a/lib/dma-debug.c
> +++ b/lib/dma-debug.c
> @@ -45,18 +45,25 @@ enum {
> dma_debug_coherent,
> };
>
> +enum map_err_types {
> + MAP_ERR_CHECK_NOT_APPLICABLE,
> + MAP_ERR_NOT_CHECKED,
> + MAP_ERR_CHECKED,
> +};
> +
> #define DMA_DEBUG_STACKTRACE_ENTRIES 5
>
> struct dma_debug_entry {
> - struct list_head list;
> - struct device *dev;
> - int type;
> - phys_addr_t paddr;
> - u64 dev_addr;
> - u64 size;
> - int direction;
> - int sg_call_ents;
> - int sg_mapped_ents;
> + struct list_head list;
> + struct device *dev;
> + int type;
> + phys_addr_t paddr;
> + u64 dev_addr;
> + u64 size;
> + int direction;
> + int sg_call_ents;
> + int sg_mapped_ents;
> + enum map_err_types map_err_type;
Something gone wild with your tabs/space. It should be only
one extra field added.
Otherwise:
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> #ifdef CONFIG_STACKTRACE
> struct stack_trace stacktrace;
> unsigned long st_entries[DMA_DEBUG_STACKTRACE_ENTRIES];
> @@ -83,6 +90,11 @@ static u32 global_disable __read_mostly;
> /* Global error count */
> static u32 error_count;
>
> +/* dma mapping error counts */
> +static u32 map_errors;
> +static u32 map_errors_not_checked;
> +static u32 unmap_errors;
> +
> /* Global error show enable*/
> static u32 show_all_errors __read_mostly;
> /* Number of errors to show */
> @@ -104,6 +116,9 @@ static struct dentry *show_num_errors_dent __read_mostly;
> static struct dentry *num_free_entries_dent __read_mostly;
> static struct dentry *min_free_entries_dent __read_mostly;
> static struct dentry *filter_dent __read_mostly;
> +static struct dentry *map_errors_dent __read_mostly;
> +static struct dentry *map_errors_not_checked_dent __read_mostly;
> +static struct dentry *unmap_errors_dent __read_mostly;
>
> /* per-driver filter related state */
>
> @@ -114,6 +129,12 @@ static struct device_driver *current_driver __read_mostly;
>
> static DEFINE_RWLOCK(driver_name_lock);
>
> +static const char *const maperr2str[] = {
> + [MAP_ERR_CHECK_NOT_APPLICABLE] = "dma map error check not applicable",
> + [MAP_ERR_NOT_CHECKED] = "dma map error not checked",
> + [MAP_ERR_CHECKED] = "dma map error checked",
> +};
> +
> static const char *type2name[4] = { "single", "page",
> "scather-gather", "coherent" };
>
> @@ -381,11 +402,12 @@ void debug_dma_dump_mappings(struct device *dev)
> list_for_each_entry(entry, &bucket->list, list) {
> if (!dev || dev == entry->dev) {
> dev_info(entry->dev,
> - "%s idx %d P=%Lx D=%Lx L=%Lx %s\n",
> + "%s idx %d P=%Lx D=%Lx L=%Lx %s %s\n",
> type2name[entry->type], idx,
> (unsigned long long)entry->paddr,
> entry->dev_addr, entry->size,
> - dir2name[entry->direction]);
> + dir2name[entry->direction],
> + maperr2str[entry->map_err_type]);
> }
> }
>
> @@ -695,6 +717,28 @@ static int dma_debug_fs_init(void)
> if (!filter_dent)
> goto out_err;
>
> + map_errors_dent = debugfs_create_u32("map_errors", 0444,
> + dma_debug_dent,
> + &map_errors);
> +
> + if (!map_errors_dent)
> + goto out_err;
> +
> + map_errors_not_checked_dent = debugfs_create_u32(
> + "map_errors_not_checked",
> + 0444,
> + dma_debug_dent,
> + &map_errors_not_checked);
> +
> + if (!map_errors_not_checked_dent)
> + goto out_err;
> +
> + unmap_errors_dent = debugfs_create_u32("unmap_errors", 0444,
> + dma_debug_dent,
> + &unmap_errors);
> + if (!unmap_errors_dent)
> + goto out_err;
> +
> return 0;
>
> out_err:
> @@ -843,13 +887,29 @@ static __init int dma_debug_entries_cmdline(char *str)
> __setup("dma_debug=", dma_debug_cmdline);
> __setup("dma_debug_entries=", dma_debug_entries_cmdline);
>
> +/* Calling dma_mapping_error() from dma-debug api will result in calling
> + debug_dma_mapping_error() - need internal mapping error routine to
> + avoid debug checks */
> +#ifndef DMA_ERROR_CODE
> +#define DMA_ERROR_CODE 0
> +#endif
> +static inline int check_mapping_error(struct device *dev, dma_addr_t dma_addr)
> +{
> + const struct dma_map_ops *ops = get_dma_ops(dev);
> + if (ops->mapping_error)
> + return ops->mapping_error(dev, dma_addr);
> +
> + return (dma_addr == DMA_ERROR_CODE);
> +}
> +
> static void check_unmap(struct dma_debug_entry *ref)
> {
> struct dma_debug_entry *entry;
> struct hash_bucket *bucket;
> unsigned long flags;
>
> - if (dma_mapping_error(ref->dev, ref->dev_addr)) {
> + if (unlikely(check_mapping_error(ref->dev, ref->dev_addr))) {
> + unmap_errors += 1;
> err_printk(ref->dev, NULL, "DMA-API: device driver tries "
> "to free an invalid DMA memory address\n");
> return;
> @@ -915,6 +975,15 @@ static void check_unmap(struct dma_debug_entry *ref)
> dir2name[ref->direction]);
> }
>
> + if (entry->map_err_type == MAP_ERR_NOT_CHECKED) {
> + err_printk(ref->dev, entry,
> + "DMA-API: device driver failed to check map error"
> + "[device address=0x%016llx] [size=%llu bytes] "
> + "[mapped as %s]",
> + ref->dev_addr, ref->size,
> + type2name[entry->type]);
> + }
> +
> hash_bucket_del(entry);
> dma_entry_free(entry);
>
> @@ -1022,8 +1091,11 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
> if (unlikely(global_disable))
> return;
>
> - if (unlikely(dma_mapping_error(dev, dma_addr)))
> + if (unlikely(check_mapping_error(dev, dma_addr))) {
> + map_errors += 1;
> + map_errors_not_checked += 1;
> return;
> + }
>
> entry = dma_entry_alloc();
> if (!entry)
> @@ -1035,6 +1107,7 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
> entry->dev_addr = dma_addr;
> entry->size = size;
> entry->direction = direction;
> + entry->map_err_type = MAP_ERR_NOT_CHECKED;
>
> if (map_single)
> entry->type = dma_debug_single;
> @@ -1050,6 +1123,35 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
> }
> EXPORT_SYMBOL(debug_dma_map_page);
>
> +void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
> +{
> + struct dma_debug_entry ref;
> + struct dma_debug_entry *entry;
> + struct hash_bucket *bucket;
> + unsigned long flags;
> +
> + if (unlikely(global_disable))
> + return;
> +
> + ref.dev = dev;
> + ref.dev_addr = dma_addr;
> + bucket = get_hash_bucket(&ref, &flags);
> + entry = bucket_find_exact(bucket, &ref);
> +
> + if (!entry) {
> + /* very likley dma-api didn't call debug_dma_map_page() or
> + debug_dma_map_page() detected mapping error */
> + if (map_errors_not_checked)
> + map_errors_not_checked -= 1;
> + goto out;
> + }
> +
> + entry->map_err_type = MAP_ERR_CHECKED;
> +out:
> + put_hash_bucket(bucket, &flags);
> +}
> +EXPORT_SYMBOL(debug_dma_mapping_error);
> +
> void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
> size_t size, int direction, bool map_single)
> {
> --
> 1.7.9.5
>
>
>
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