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[80.230.31.118]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47be27b28a7sm638896415e9.12.2025.12.30.02.16.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Dec 2025 02:16:33 -0800 (PST) Date: Tue, 30 Dec 2025 05:16:29 -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 13/13] vsock/virtio: reorder fields to reduce struct padding Message-ID: 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" Reorder struct virtio_vsock fields to place the DMA buffer (event_list) last. This eliminates the need for __dma_from_device_aligned_end padding after the DMA buffer, since struct tail padding naturally protects it, making the struct a bit smaller. Size reduction estimation when ARCH_DMA_MINALIGN=3D128: - event_list is 32 bytes - removing _end saves up to 128-32=3D96 bytes padding to align next field Signed-off-by: Michael S. Tsirkin --- net/vmw_vsock/virtio_transport.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transp= ort.c index f1589db5d190..2e34581f1143 100644 --- a/net/vmw_vsock/virtio_transport.c +++ b/net/vmw_vsock/virtio_transport.c @@ -60,10 +60,7 @@ struct virtio_vsock { */ struct mutex event_lock; bool event_run; - __dma_from_device_aligned_begin - struct virtio_vsock_event event_list[8]; =20 - __dma_from_device_aligned_end u32 guest_cid; bool seqpacket_allow; =20 @@ -77,6 +74,10 @@ struct virtio_vsock { */ struct scatterlist *out_sgs[MAX_SKB_FRAGS + 1]; struct scatterlist out_bufs[MAX_SKB_FRAGS + 1]; + + /* DMA buffer - must be last, aligned for non-cache-coherent DMA */ + __dma_from_device_aligned_begin + struct virtio_vsock_event event_list[8]; }; =20 static u32 virtio_transport_get_local_cid(void) --=20 MST