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Tsirkin" , Petr Tesarik , Jonathan Corbet , Shuah Khan , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Jason Gunthorpe , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Joerg Roedel , Will Deacon , Andrew Morton Cc: iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, virtualization@lists.linux.dev, linux-rdma@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260316-dma-debug-overlap-v3-0-1dde90a7f08b@nvidia.com> <20260316-dma-debug-overlap-v3-4-1dde90a7f08b@nvidia.com> Content-Language: en-US From: Randy Dunlap In-Reply-To: <20260316-dma-debug-overlap-v3-4-1dde90a7f08b@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: k33xsxzyx3upek15a7xarrgmg7dkdm43 X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: 11911180010 X-HE-Tag: 1773688669-452559 X-HE-Meta: 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 bRshnikj xDPyx3zTNZEgP50kGFaT3z0cZmZaYwVpTxwSoyhbyTlzCwMQUmNsh/IY2/XP2tqKYrn9CBzQgd45qCKUoXzCw8q8Dj6XSjgRKl6/c6EZ6jaj67ANVZ38guyNNXYuimCqUCFctJefPuTFk5auP2mclU+ViV7O2aBvKjsZhVKWCvBOO0ql+QqX/VvqO2oTaYyEfqzoJSlzEsQXKBx8pZDwytQECDeggT/W4wjp9Z8jfSnHmt92HDyUlOWMg+VgqIaHO6wba Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/16/26 12:06 PM, Leon Romanovsky wrote: > diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst > index 48cfe86cc06d7..441bdc9d08318 100644 > --- a/Documentation/core-api/dma-attributes.rst > +++ b/Documentation/core-api/dma-attributes.rst > @@ -163,3 +163,19 @@ data corruption. > > All mappings that share a cache line must set this attribute to suppress DMA > debug warnings about overlapping mappings. > + > +DMA_ATTR_REQUIRE_COHERENT > +------------------------- > + > +DMA mapping requests with the DMA_ATTR_REQUIRE_COHERENT fail on any > +system where SWIOTLB or cache management is required. This should only > +be used to support uAPI designs that require continuous HW DMA > +coherence with userspace processes, for example RDMA and DRM. At a > +minimum the memory being mapped must be userspace memory from > +pin_user_pages() or similar. > + > +Drivers should consider using dma_mmap_pages() instead of this > +interface when building their uAPIs, when possible. > + > +It must never be used in an in-kernel driver that only works with > +kernal memory. kernel -- ~Randy