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[2a00:1028:83b8:1e7a:3010:3bd6:8521:caf1]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4324e9ba877sm100563291f8f.0.2026.01.05.01.40.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 Jan 2026 01:40:39 -0800 (PST) Date: Mon, 5 Jan 2026 10:40:36 +0100 From: Petr Tesarik To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, Cong Wang , Jonathan Corbet , Olivia Mackall , Herbert Xu , Jason Wang , Paolo Bonzini , Stefan Hajnoczi , Eugenio =?UTF-8?B?UMOpcmV6?= , "James E.J. Bottomley" , "Martin K. Petersen" , Gerd Hoffmann , Xuan Zhuo , Marek Szyprowski , Robin Murphy , Stefano Garzarella , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Leon Romanovsky , Jason Gunthorpe , Bartosz Golaszewski , linux-doc@vger.kernel.org, linux-crypto@vger.kernel.org, virtualization@lists.linux.dev, linux-scsi@vger.kernel.org, iommu@lists.linux.dev, kvm@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH v2 01/15] dma-mapping: add __dma_from_device_group_begin()/end() Message-ID: <20260105104036.09a77f13@mordecai> In-Reply-To: <19163086d5e4704c316f18f6da06bc1c72968904.1767601130.git.mst@redhat.com> References: <19163086d5e4704c316f18f6da06bc1c72968904.1767601130.git.mst@redhat.com> X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-suse-linux-gnu) Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 5 Jan 2026 03:22:54 -0500 "Michael S. Tsirkin" wrote: > When a structure contains a buffer that DMA writes to alongside fields > that the CPU writes to, cache line sharing between the DMA buffer and > CPU-written fields can cause data corruption on non-cache-coherent > platforms. > > Add __dma_from_device_group_begin()/end() annotations to ensure proper > alignment to prevent this: > > struct my_device { > spinlock_t lock1; > __dma_from_device_group_begin(); > char dma_buffer1[16]; > char dma_buffer2[16]; > __dma_from_device_group_end(); > spinlock_t lock2; > }; > > Signed-off-by: Michael S. Tsirkin LGTM. I'm not formally a reviewer, but FWIW: Reviewed-by: Petr Tesarik > --- > include/linux/dma-mapping.h | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index aa36a0d1d9df..29ad2ce700f0 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -7,6 +7,7 @@ > #include > #include > #include > +#include > > /** > * List of possible attributes associated with a DMA mapping. The semantics > @@ -703,6 +704,18 @@ static inline int dma_get_cache_alignment(void) > } > #endif > > +#ifdef ARCH_HAS_DMA_MINALIGN > +#define ____dma_from_device_aligned __aligned(ARCH_DMA_MINALIGN) > +#else > +#define ____dma_from_device_aligned > +#endif > +/* Mark start of DMA buffer */ > +#define __dma_from_device_group_begin(GROUP) \ > + __cacheline_group_begin(GROUP) ____dma_from_device_aligned > +/* Mark end of DMA buffer */ > +#define __dma_from_device_group_end(GROUP) \ > + __cacheline_group_end(GROUP) ____dma_from_device_aligned > + > static inline void *dmam_alloc_coherent(struct device *dev, size_t size, > dma_addr_t *dma_handle, gfp_t gfp) > {