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[PATCH v2] dma/contiguous: Fix broken build

by Maxime Ripard

Commit 3a236f6a5cf2 ("dma: contiguous: Turn heap registration logic around") didn't remove one last call to dma_heap_cma_register_heap() that it removed, thus breaking the build. That last call is in dma_contiguous_reserve(), to handle the registration of the default CMA region heap instance. The default CMA region instance is already somewhat handled by retrieving it through the dev_get_cma_area() call in the CMA heap driver. However, since commit 854acbe75ff4 ("dma-buf: heaps: Give default CMA heap a fixed name"), we will create two heap instances for the CMA default region. The first one is always called "default_cma_region", and is the one handled by the call to dev_get_cma_area() mentioned earlier. The second one is the name it used to have prior to that last commit for backward compatibility. In the case where the default CMA region is defined in the DT, then that region is registered through rmem_cma_setup() and that region is added to the list of CMA regions to create a CMA heap instance for. In the case where the default CMA region is not defined in the DT though used to be the case covered by the now removed dma_heap_cma_register_heap() in dma_contiguous_reserve(). If we only remove the call to dma_heap_cma_register_heap(), then the legacy name of the CMA heap will not be registered anymore. We thus need to replace that call with a call to rmem_cma_insert_area() to make sure we queue this instance, if created, to create a heap instance. Once that call to dma_heap_cma_register_heap() replaced, we can also remove the now unused function definition, its now empty header, and all includes of this header. Fixes: 3a236f6a5cf2 ("dma: contiguous: Turn heap registration logic around") Reported-by: Mark Brown <broonie(a)kernel.org> Closes: https://lore.kernel.org/linux-next/acbjaDJ1a-YQC64d@sirena.co.uk/ Signed-off-by: Maxime Ripard <mripard(a)kernel.org> --- Changes in v2: - Fix creation of the CMA heap instance with the legacy name when not declared in the DT. - Link to v1: https://lore.kernel.org/r/20260330-dma-build-fix-v1-1-748b64f0d8af@kernel.o… --- drivers/dma-buf/heaps/cma_heap.c | 1 - include/linux/dma-buf/heaps/cma.h | 16 ---------------- kernel/dma/contiguous.c | 14 +++++++++++--- 3 files changed, 11 insertions(+), 20 deletions(-) diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index 7216a14262b04bb6130ddf26b7d009f7d15b03fd..9a8b36bc929f6daa483a0139a2919d95127e0d23 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -12,11 +12,10 @@ #define pr_fmt(fmt) "cma_heap: " fmt #include <linux/cma.h> #include <linux/dma-buf.h> -#include <linux/dma-buf/heaps/cma.h> #include <linux/dma-heap.h> #include <linux/dma-map-ops.h> #include <linux/err.h> #include <linux/highmem.h> #include <linux/io.h> diff --git a/include/linux/dma-buf/heaps/cma.h b/include/linux/dma-buf/heaps/cma.h deleted file mode 100644 index e751479e21e703e24a5f799b4a7fc8bd0df3c1c4..0000000000000000000000000000000000000000 --- a/include/linux/dma-buf/heaps/cma.h +++ /dev/null @@ -1,16 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0 */ -#ifndef DMA_BUF_HEAP_CMA_H_ -#define DMA_BUF_HEAP_CMA_H_ - -struct cma; - -#ifdef CONFIG_DMABUF_HEAPS_CMA -int dma_heap_cma_register_heap(struct cma *cma); -#else -static inline int dma_heap_cma_register_heap(struct cma *cma) -{ - return 0; -} -#endif // CONFIG_DMABUF_HEAPS_CMA - -#endif // DMA_BUF_HEAP_CMA_H_ diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index ad50512d71d3088a73e4b1ac02d6e6122374888e..d5d15983060c5c54744d6a63f2b591e1a3455b86 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -40,11 +40,10 @@ #include <asm/page.h> #include <linux/memblock.h> #include <linux/err.h> #include <linux/sizes.h> -#include <linux/dma-buf/heaps/cma.h> #include <linux/dma-map-ops.h> #include <linux/cma.h> #include <linux/nospec.h> #ifdef CONFIG_CMA_SIZE_MBYTES @@ -217,10 +216,19 @@ static void __init dma_numa_cma_reserve(void) static inline void __init dma_numa_cma_reserve(void) { } #endif +#ifdef CONFIG_OF_RESERVED_MEM +static int rmem_cma_insert_area(struct cma *cma); +#else +static inline int rmem_cma_insert_area(struct cma *cma) +{ + return 0; +} +#endif + /** * dma_contiguous_reserve() - reserve area(s) for contiguous memory handling * @limit: End address of the reserved memory (optional, 0 for any). * * This function reserves memory from early allocator. It should be @@ -271,13 +279,13 @@ void __init dma_contiguous_reserve(phys_addr_t limit) &dma_contiguous_default_area, fixed); if (ret) return; - ret = dma_heap_cma_register_heap(dma_contiguous_default_area); + ret = rmem_cma_insert_area(dma_contiguous_default_area); if (ret) - pr_warn("Couldn't register default CMA heap."); + pr_warn("Couldn't queue default CMA region for heap creation."); } } void __weak dma_contiguous_early_fixup(phys_addr_t base, unsigned long size) --- base-commit: 6c683d5b1903a14e362c9f1628ce9fe61eac35e7 change-id: 20260330-dma-build-fix-706a4feb0e0f Best regards, -- Maxime Ripard <mripard(a)kernel.org>

10 hours, 15 minutes

Re: [PATCH RESEND] dma-fence: Dereference correct dma_fence in dma_fence_chain_find_seqno()

by Christian König

On 3/28/26 11:26, Li Ming wrote: > > 在 2026/3/28 02:47, Li Ming 写道: >> dma_fence_chain_find_seqno() uses dma_fence_chain_for_each() to walk a >> given dma_fence_chain. dma_fence_chain_for_each() always holds a >> reference for the current fence during iteration. The reference must >> be dropped after breaking out. Instead of dereferencing the last fence >> as intended, dma_fence_chain_find_seqno() incorrectly dereferences the >> first fence in the chain. >> >> Fixes: 7bf60c52e093 ("dma-buf: add new dma_fence_chain container v7") >> Signed-off-by: Li Ming <ming.li(a)zohomail.com> >> --- >> drivers/dma-buf/dma-fence-chain.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c >> index a8a90acf4f34..71fa173aef13 100644 >> --- a/drivers/dma-buf/dma-fence-chain.c >> +++ b/drivers/dma-buf/dma-fence-chain.c >> @@ -103,7 +103,7 @@ int dma_fence_chain_find_seqno(struct dma_fence **pfence, uint64_t seqno) >> to_dma_fence_chain(*pfence)->prev_seqno < seqno) >> break; >> } >> - dma_fence_put(&chain->base); >> + dma_fence_put(*pfence); >> return 0; >> } >> >> --- >> base-commit: c369299895a591d96745d6492d4888259b004a9e >> change-id: 20260327-fix_dma_fence_chain_find_seqno-7adea64efe01 >> >> Best regards, > > After looking deeper into this issue, it is not a bug. > > Seems like this function requires that caller needs to hold the reference of the give fence before calling it. When pfence changed, need to transfer the reference from the original fence to the new fence. That is why it releases the reference for the original fence in the end. Yeah exactly that. We have documented the behavior in the kerneldoc: * Advance the fence pointer to the chain node which will signal this sequence * number. But that is somehow not enough. If you have suggestions how to improve the comments then please speak up. This patch has been suggested as "fix" numerous times. Regards, Christian. > > Sorry to make this noise. > > > Ming >

10 hours, 26 minutes

[PATCH] dma/contiguous: Fix broken build

by Maxime Ripard

12 hours, 24 minutes

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Re: [RFC v2 PATCH 09/10] vfio/pci: Add mmap() attributes to DMABUF feature

by Jason Gunthorpe

On Thu, Mar 12, 2026 at 11:46:07AM -0700, Matt Evans wrote: > A new field is reserved in vfio_device_feature_dma_buf.flags to > request CPU-facing memory type attributes for mmap()s of the buffer. > Add a flag VFIO_DEVICE_FEATURE_DMA_BUF_ATTR_WC, which results in WC > PTEs for the DMABUF's BAR region. This seems very straightforward, I like it Did I get it right that the idea is the user would request a dmabuf with these flags and then mmap the dmabuf? Jason

14 hours, 31 minutes

Re: [RFC v2 PATCH 02/10] vfio/pci: Clean up DMABUFs before disabling function

by Jason Gunthorpe

On Thu, Mar 12, 2026 at 11:46:00AM -0700, Matt Evans wrote: > On device shutdown, make vfio_pci_core_close_device() call > vfio_pci_dma_buf_cleanup() before the function is disabled via > vfio_pci_core_disable(). This ensures that all access via DMABUFs is > revoked before the function's BARs become inaccessible. > > This fixes an issue where, if the function is disabled first, a tiny > window exists in which the function's MSE is cleared and yet BARs > could still be accessed via the DMABUF. The resources would also be > freed and up for grabs by a different driver. > > Fixes: 5d74781ebc86c ("vfio/pci: Add dma-buf export support for MMIO regions") > Signed-off-by: Matt Evans <mattev(a)meta.com> > --- > drivers/vfio/pci/vfio_pci_core.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) This seems like it should not be RFC and it should go to stable? The normal mmaps are cleaned because they hold the file open while they exist, dmabuf upends that and it does need zapping early. Reviewed-by: Jason Gunthorpe <jgg(a)nvidia.com> Jason

14 hours, 34 minutes

Re: [PATCH] dma-fence: Dereference correct dma_fence in dma_fence_chain_find_seqno()

by Christian König

On 3/27/26 15:33, Li Ming wrote: > dma_fence_chain_find_seqno() uses dma_fence_chain_for_each() to walk a > given dma_fence_chain. dma_fence_chain_for_each() always holds a > reference for the current fence during iteration. The reference must > be dropped after breaking out. Instead of dereferencing the last fence > as intended, dma_fence_chain_find_seqno() incorrectly dereferences the > first fence in the chain. Well once more: Absolutely clear NAK and please search the mailing list for similar changes before you send a patch out. The existing code is perfectly correct and I can't count how often I had to reject that patch. I think the functionality is obvious but it looks like we really need to add a comment here. Regards, Christian. > > Fixes: 7bf60c52e093 ("dma-buf: add new dma_fence_chain container v7") > Signed-off-by: Li Ming <ming.li(a)zohomail.com> > --- > drivers/dma-buf/dma-fence-chain.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c > index a8a90acf4f34..71fa173aef13 100644 > --- a/drivers/dma-buf/dma-fence-chain.c > +++ b/drivers/dma-buf/dma-fence-chain.c > @@ -103,7 +103,7 @@ int dma_fence_chain_find_seqno(struct dma_fence **pfence, uint64_t seqno) > to_dma_fence_chain(*pfence)->prev_seqno < seqno) > break; > } > - dma_fence_put(&chain->base); > + dma_fence_put(*pfence); > > return 0; > } > > --- > base-commit: c369299895a591d96745d6492d4888259b004a9e > change-id: 20260327-fix_dma_fence_chain_find_seqno-7adea64efe01 > > Best regards, > -- > Li Ming <ming.li(a)zohomail.com> >

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