linux/kernel/dma/debug.c, branch v5.17

dma-debug: teach add_dma_entry() about DMA_ATTR_SKIP_CPU_SYNC

2021-10-18T10:46:45Z

Mapping something twice should be possible as long as, DMA_ATTR_SKIP_CPU_SYNC is passed to the strictly speaking second relevant mapping operation (that attempts to map the same thing). So, don't issue a warning if the specified condition is met in add_dma_entry(). Signed-off-by: Hamza Mahfooz Signed-off-by: Christoph Hellwig

dma-debug: fix sg checks in debug_dma_map_sg()

2021-10-11T11:43:31Z

The following warning occurred sporadically on s390: DMA-API: nvme 0006:00:00.0: device driver maps memory from kernel text or rodata [addr=0000000048cc5e2f] [len=131072] WARNING: CPU: 4 PID: 825 at kernel/dma/debug.c:1083 check_for_illegal_area+0xa8/0x138 It is a false-positive warning, due to broken logic in debug_dma_map_sg(). check_for_illegal_area() checks for overlay of sg elements with kernel text or rodata. It is called with sg_dma_len(s) instead of s->length as parameter. After the call to ->map_sg(), sg_dma_len() will contain the length of possibly combined sg elements in the DMA address space, and not the individual sg element length, which would be s->length. The check will then use the physical start address of an sg element, and add the DMA length for the overlap check, which could result in the false warning, because the DMA length can be larger than the actual single sg element length. In addition, the call to check_for_illegal_area() happens in the iteration over mapped_ents, which will not include all individual sg elements if any of them were combined in ->map_sg(). Fix this by using s->length instead of sg_dma_len(s). Also put the call to check_for_illegal_area() in a separate loop, iterating over all the individual sg elements ("nents" instead of "mapped_ents"). While at it, as suggested by Robin Murphy, also move check_for_stack() inside the new loop, as it is similarly concerned with validating the individual sg elements. Link: https://lore.kernel.org/lkml/20210705185252.4074653-1-gerald.schaefer@linux.ibm.com Fixes: 884d05970bfb ("dma-debug: use sg_dma_len accessor") Signed-off-by: Gerald Schaefer Signed-off-by: Christoph Hellwig

dma-debug: prevent an error message from causing runtime problems

2021-09-13T16:29:24Z

For some drivers, that use the DMA API. This error message can be reached several millions of times per second, causing spam to the kernel's printk buffer and bringing the CPU usage up to 100% (so, it should be rate limited). However, since there is at least one driver that is in the mainline and suffers from the error condition, it is more useful to err_printk() here instead of just rate limiting the error message (in hopes that it will make it easier for other drivers that suffer from this issue to be spotted). Link: https://lkml.kernel.org/r/fd67fbac-64bf-f0ea-01e1-5938ccfab9d0@arm.com Reported-by: Jeremy Linton Signed-off-by: Hamza Mahfooz Signed-off-by: Christoph Hellwig

dma-debug: fix debugfs initialization order

2021-08-09T15:06:11Z

Due to link order, dma_debug_init is called before debugfs has a chance to initialize (via debugfs_init which also happens in the core initcall stage), so the directories for dma-debug are never created. Decouple dma_debug_fs_init from dma_debug_init and defer its init until core_initcall_sync (after debugfs has been initialized) while letting dma-debug initialization occur as soon as possible to catch any early mappings, as suggested in [1]. [1] https://lore.kernel.org/linux-iommu/YIgGa6yF%2Fadg8OSN@kroah.com/ Fixes: 15b28bbcd567 ("dma-debug: move initialization to common code") Signed-off-by: Anthony Iliopoulos Signed-off-by: Christoph Hellwig

dma-debug: use memory_intersects() directly

2021-08-09T15:03:17Z

There is already a memory_intersects() helper in sections.h, use memory_intersects() directly instead of private overlap(). Signed-off-by: Kefeng Wang Signed-off-by: Christoph Hellwig

dma-debug: report -EEXIST errors in add_dma_entry

2021-06-22T06:15:47Z

Since, overlapping mappings are not supported by the DMA API we should report an error if active_cacheline_insert returns -EEXIST. Suggested-by: Dan Williams Signed-off-by: Hamza Mahfooz Signed-off-by: Christoph Hellwig

dma-mapping: move dma-debug.h to kernel/dma/

2020-10-06T05:07:05Z

Most of dma-debug.h is not required by anything outside of kernel/dma. Move the four declarations needed by dma-mappin.h or dma-ops providers into dma-mapping.h and dma-map-ops.h, and move the remainder of the file to kernel/dma/debug.h. Signed-off-by: Christoph Hellwig

dma-debug: convert comma to semicolon

2020-09-21T14:48:38Z

Replace a comma between expression statements by a semicolon. Signed-off-by: Xu Wang Signed-off-by: Christoph Hellwig

dma-debug: remove most exports

2020-09-11T06:13:12Z

Now that the main dma mapping entry points are out of line most of the symbols in dma-debug.c can only be called from built-in code. Remove the unused exports. Signed-off-by: Christoph Hellwig Reviewed-by: Robin Murphy

dma-debug: remove debug_dma_assert_idle() function

2020-08-14T22:22:43Z

This remoes the code from the COW path to call debug_dma_assert_idle(), which was added many years ago. Google shows that it hasn't caught anything in the 6+ years we've had it apart from a false positive, and Hugh just noticed how it had a very unfortunate spinlock serialization in the COW path. He fixed that issue the previous commit (a85ffd59bd36: "dma-debug: fix debug_dma_assert_idle(), use rcu_read_lock()"), but let's see if anybody even notices when we remove this function entirely. NOTE! We keep the dma tracking infrastructure that was added by the commit that introduced it. Partly to make it easier to resurrect this debug code if we ever deside to, and partly because that tracking by pfn and offset looks quite reasonable. The problem with this debug code was simply that it was expensive and didn't seem worth it, not that it was wrong per se. Acked-by: Dan Williams Acked-by: Christoph Hellwig Signed-off-by: Linus Torvalds