Re: [PATCH v3 0/8] RDMA: Enable operation with DMA debug enabled

Marek Szyprowski
2026-03-20T11:08:43Z

Hi Leon,

On 18.03.2026 09:18, Leon Romanovsky wrote:
> On Wed, Mar 18, 2026 at 09:03:00AM +0100, Marek Szyprowski wrote:
>> On 17.03.2026 20:05, Leon Romanovsky wrote:
>>> On Mon, Mar 16, 2026 at 09:06:44PM +0200, Leon Romanovsky wrote:
>>>> Add a new DMA_ATTR_REQUIRE_COHERENT attribute to the DMA API to mark
>>>> mappings that must run on a DMA‑coherent system. Such buffers cannot
>>>> use the SWIOTLB path, may overlap with CPU caches, and do not depend on
>>>> explicit cache flushing.
>>>>
>>>> Mappings using this attribute are rejected on systems where cache
>>>> side‑effects could lead to data corruption, and therefore do not need
>>>> the cache‑overlap debugging logic. This series also includes fixes for
>>>> DMA_ATTR_CPU_CACHE_CLEAN handling.
>>>> Thanks.
>>> <...>
>>>
>>>> ---
>>>> Leon Romanovsky (8):
>>>> dma-debug: Allow multiple invocations of overlapping entries
>>>> dma-mapping: handle DMA_ATTR_CPU_CACHE_CLEAN in trace output
>>>> dma-mapping: Clarify valid conditions for CPU cache line overlap
>>>> dma-mapping: Introduce DMA require coherency attribute
>>>> dma-direct: prevent SWIOTLB path when DMA_ATTR_REQUIRE_COHERENT is set
>>>> iommu/dma: add support for DMA_ATTR_REQUIRE_COHERENT attribute
>>>> RDMA/umem: Tell DMA mapping that UMEM requires coherency
>>>> mm/hmm: Indicate that HMM requires DMA coherency
>>>>
>>>> Documentation/core-api/dma-attributes.rst | 38 ++++++++++++++++++++++++-------
>>>> drivers/infiniband/core/umem.c | 5 ++--
>>>> drivers/iommu/dma-iommu.c | 21 +++++++++++++----
>>>> drivers/virtio/virtio_ring.c | 10 ++++----
>>>> include/linux/dma-mapping.h | 15 ++++++++----
>>>> include/trace/events/dma.h | 4 +++-
>>>> kernel/dma/debug.c | 9 ++++----
>>>> kernel/dma/direct.h | 7 +++---
>>>> kernel/dma/mapping.c | 6 +++++
>>>> mm/hmm.c | 4 ++--
>>>> 10 files changed, 86 insertions(+), 33 deletions(-)
>>> Marek,
>>>
>>> Despite the "RDMA ..." tag in the subject, the diffstat clearly shows that
>>> you are the appropriate person to take this patch.
>> I plan to take the first 2 patches to the dma-mapping-fixes branch
>> (v7.0-rc) and the next to dma-mapping-for-next. Should I also take the
>> RDMA and HMM patches, or do You want a stable branch for merging them
>> via respective subsystem trees?
> I suggest taking all patches into the -fixes branch, as the "RDMA/..." patch
> also resolves the dmesg splat. With -fixes, there is no need to worry about
> a shared branch since we do not expect merge conflicts in that area.
>
> If you still prefer to split the series between -fixes and -next, it would be
> better to use a shared branch in that case. There are patches on the RDMA
> list targeted for -next that touch ib_umem_get().

Okay, I will merge all patches to the -fixes branch then.

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland