[PATCH v2] dma-debug: New interfaces to debug dma mapping errors
Konrad Rzeszutek Wilk
konrad.wilk at oracle.com
Wed Sep 26 13:12:10 UTC 2012
> 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.
>
> The following existing dma-debug APIs are changed to support this feature:
>
> debug_dma_map_page():
> Increments dma_map_errors and dma_map_errors_not_checked error totals
> for the system when dma_addr is invalid. Please note that this routine
> can no longer call dma_mapping_error(), because of the newly added
> debug_dma_mapping_error() interface. Calling this routine at the time
> dma error unchecked state is registered, will not help if state gets
> changed right away.
>
> check_unmap():
> This is an existing internal routine that checks for various mapping
> errors. Changed to increment system wide dma_unmap_errors, when a
> device requests an invalid address to be unmapped. Please note that
> this routine can no longer call dma_mapping_error(), because of the
> newly added debug_dma_mapping_error() interface. Calling
> dma_mapping_error() from this routine will change the dma map error
> flag erroneously.
>
> 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.
Thanks for improving this patch. It is looking more and more ready for
the kernel. With that in mind, I've some comments below.
>
> 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 at hp.com>
> ---
> Documentation/DMA-API.txt | 13 +++++
> arch/x86/include/asm/dma-mapping.h | 1 +
> include/linux/dma-debug.h | 7 +++
> lib/dma-debug.c | 92 ++++++++++++++++++++++++++++++++++--
> 4 files changed, 109 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
> index 66bd97a..59d58b9 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/dma_map_errors This file is read-only and shows the total
> + number of dma mapping errors detected.
> +
> + dma-api/dma_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/dma_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..70724a5 100644
> --- a/lib/dma-debug.c
> +++ b/lib/dma-debug.c
> @@ -57,6 +57,7 @@ struct dma_debug_entry {
> int direction;
> int sg_call_ents;
> int sg_mapped_ents;
> + int dma_map_error_flag;
I don't think you need 'dma_map' as a prefix a this is in an
dma_debug structure. Perhaps 'map_error_cnt' ?
But looking at the implementation this is actually an enum?
Can you do this instead:
enum map_err_type map_err_type;
?
> #ifdef CONFIG_STACKTRACE
> struct stack_trace stacktrace;
> unsigned long st_entries[DMA_DEBUG_STACKTRACE_ENTRIES];
> @@ -83,6 +84,11 @@ static u32 global_disable __read_mostly;
> /* Global error count */
> static u32 error_count;
>
> +/* dma mapping error counts */
> +static u32 dma_map_errors;
> +static u32 dma_map_errors_not_checked;
> +static u32 dma_unmap_errors;
s/dma//
> +
> /* Global error show enable*/
> static u32 show_all_errors __read_mostly;
> /* Number of errors to show */
> @@ -104,6 +110,9 @@ 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 *dma_map_errors_dent __read_mostly;
> +static struct dentry *dma_map_errors_not_checked_dent __read_mostly;
> +static struct dentry *dma_unmap_errors_dent __read_mostly;
Ditto.
>
> /* per-driver filter related state */
>
> @@ -120,6 +129,15 @@ static const char *type2name[4] = { "single", "page",
> static const char *dir2name[4] = { "DMA_BIDIRECTIONAL", "DMA_TO_DEVICE",
> "DMA_FROM_DEVICE", "DMA_NONE" };
>
> +enum {
> + dma_map_error_check_not_applicable,
> + dma_map_error_not_checked,
> + dma_map_error_checked,
> +};
s/dma//
s/error/err//
And perhaps make them uppercase?
Can you name the enum? Say 'map_err_types'
> +static const char *maperr2str[3] = { "dma map error check not applicable",
> + "dma map error not checked",
> + "dma map error checked" };
> +
Just do this:
static const char *const names[] = {
[err_check_na] = {"check n/a"},
[err_not_checked] = {"not checked"},
.. snip..
};
That way you don't have to worry about the size and can just
use ARRAY_SIZE(names) to check for valid enum size.
> /* little merge helper - remove it after the merge window */
> #ifndef BUS_NOTIFY_UNBOUND_DRIVER
> #define BUS_NOTIFY_UNBOUND_DRIVER 0x0005
> @@ -381,11 +399,12 @@ 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->dma_map_error_flag]);
> }
> }
>
> @@ -695,6 +714,28 @@ static int dma_debug_fs_init(void)
> if (!filter_dent)
> goto out_err;
>
> + dma_map_errors_dent = debugfs_create_u32("dma_map_errors", 0444,
Just call it 'map_errors'
> + dma_debug_dent,
> + &dma_map_errors);
> +
> + if (!dma_map_errors_dent)
> + goto out_err;
> +
> + dma_map_errors_not_checked_dent = debugfs_create_u32(
> + "dma_map_errors_not_checked",
Ditto. s/dma//
> + 0444,
> + dma_debug_dent,
> + &dma_map_errors_not_checked);
> +
> + if (!dma_map_errors_not_checked_dent)
> + goto out_err;
> +
> + dma_unmap_errors_dent = debugfs_create_u32("dma_unmap_errors", 0444,
s/dma//
> + dma_debug_dent,
> + &dma_unmap_errors);
> + if (!dma_unmap_errors_dent)
> + goto out_err;
> +
This whole function could use a a loop to set this up instead of doing
one by one... But that is another patch that can be done later.
> return 0;
>
> out_err:
> @@ -849,7 +890,8 @@ static void check_unmap(struct dma_debug_entry *ref)
> struct hash_bucket *bucket;
> unsigned long flags;
>
> - if (dma_mapping_error(ref->dev, ref->dev_addr)) {
> + if (ref->dev_addr == DMA_ERROR_CODE) {
The DMA_ERROR_CODE is not exported on every architecture. Worst yet,
it is not used universally on all IOMMUs - if you look in the GART
(gart_mapping_error) it does not check for the DMA_ERROR_CODE but for
its own bad_dma_addr address. I think using the dma_mapping_errors here
is still a good idea.
> + dma_unmap_errors += 1;
> err_printk(ref->dev, NULL, "DMA-API: device driver tries "
> "to free an invalid DMA memory address\n");
> return;
> @@ -915,6 +957,15 @@ static void check_unmap(struct dma_debug_entry *ref)
> dir2name[ref->direction]);
> }
>
> + if (entry->dma_map_error_flag == dma_map_error_not_checked) {
Wait. Aren't you using dma_map_error_flag to only be up to 3 - as you
are using it to lookup in the string table for its proper name?
Perhaps the string table lookup should use a different flag??
> + 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 +1073,11 @@ 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 (dma_addr == DMA_ERROR_CODE) {
Ditto
> + dma_map_errors += 1;
> + dma_map_errors_not_checked += 1;
> return;
> + }
>
> entry = dma_entry_alloc();
> if (!entry)
> @@ -1035,6 +1089,7 @@ 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->dma_map_error_flag = dma_map_error_not_checked;
So if it is greater than three, then maperr2str[entry->dma_map_error_flag] is going
to blow up, right?
>
> if (map_single)
> entry->type = dma_debug_single;
> @@ -1050,6 +1105,35 @@ 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;
> +
> + if (dma_addr == DMA_ERROR_CODE) {
Don't use that... Just the IOMMUs' dma_mapping_error call..
> + dma_map_errors_not_checked -= 1;
Should you check in case the user calls dma_mapping_error more than once on
the same dma_addr?
> + 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() */
Ok, so should we re-adjust dma_map_errors_not_checked? Or we
don't care?
> + goto out;
> +
> + entry->dma_map_error_flag = dma_map_error_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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