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[80.230.31.118]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47be27b0d5asm646323275e9.13.2025.12.30.02.16.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Dec 2025 02:16:24 -0800 (PST) Date: Tue, 30 Dec 2025 05:16:21 -0500 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: 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 , Petr Tesarik , Leon Romanovsky , Jason Gunthorpe , 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: [PATCH RFC 11/13] virtio-rng: fix DMA alignment for data buffer Message-ID: <318c48915a52f1739c23d46b2b99e3a51c7139de.1767089672.git.mst@redhat.com> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The data buffer in struct virtrng_info is used for DMA_FROM_DEVICE via virtqueue_add_inbuf() and shares cachelines with the adjacent CPU-written fields (data_avail, data_idx). The device writing to the DMA buffer and the CPU writing to adjacent fields could corrupt each other's data on non-cache-coherent platforms. Add __dma_from_device_aligned_begin annotation to place these in distinct cache lines. Signed-off-by: Michael S. Tsirkin --- drivers/char/hw_random/virtio-rng.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/v= irtio-rng.c index dd998f4fe4f2..fb3c57bee3b1 100644 --- a/drivers/char/hw_random/virtio-rng.c +++ b/drivers/char/hw_random/virtio-rng.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include =20 @@ -28,6 +29,7 @@ struct virtrng_info { unsigned int data_avail; unsigned int data_idx; /* minimal size returned by rng_buffer_size() */ + __dma_from_device_aligned_begin #if SMP_CACHE_BYTES < 32 u8 data[32]; #else --=20 MST