linux-kernel - [PATCH v3 15/15] vsock/virtio: reorder fields to reduce padding

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Message-ID: <ce44f61af415521e00ab7492aa16d3d19f00bd5e.1769632071.git.mst@redhat.com>
Date: Wed, 28 Jan 2026 15:31:21 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: linux-kernel@...r.kernel.org, Cong Wang <xiyou.wangcong@...il.com>,
	Jonathan Corbet <corbet@....net>,
	Olivia Mackall <olivia@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Jason Wang <jasowang@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	"James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Robin Murphy <robin.murphy@....com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, Petr Tesarik <ptesarik@...e.com>,
	Leon Romanovsky <leon@...nel.org>, Jason Gunthorpe <jgg@...pe.ca>,
	Bartosz Golaszewski <brgl@...nel.org>, linux-doc@...r.kernel.org,
	linux-crypto@...r.kernel.org, virtualization@...ts.linux.dev,
	linux-scsi@...r.kernel.org, iommu@...ts.linux.dev,
	kvm@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH v3 15/15] vsock/virtio: reorder fields to reduce padding

Reorder struct virtio_vsock fields to place the DMA buffer (event_list)
last. This eliminates the padding from aligning the struct size on
ARCH_DMA_MINALIGN.

Suggested-by: Stefano Garzarella <sgarzare@...hat.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---

changes from v2:
	move event_lock and event_run too, to keep
	event things logically together, as suggested by
	Stefano Garzarella.

Note: this is the only change in v3 and it's cosmetic, so I am
not reposting the whole patchset.


 net/vmw_vsock/virtio_transport.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index 999a0839726a..b333a7591b26 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -55,15 +55,6 @@ struct virtio_vsock {
 	int rx_buf_nr;
 	int rx_buf_max_nr;
 
-	/* The following fields are protected by event_lock.
-	 * vqs[VSOCK_VQ_EVENT] must be accessed with event_lock held.
-	 */
-	struct mutex event_lock;
-	bool event_run;
-	__dma_from_device_group_begin();
-	struct virtio_vsock_event event_list[8];
-	__dma_from_device_group_end();
-
 	u32 guest_cid;
 	bool seqpacket_allow;
 
@@ -77,6 +68,15 @@ struct virtio_vsock {
 	 */
 	struct scatterlist *out_sgs[MAX_SKB_FRAGS + 1];
 	struct scatterlist out_bufs[MAX_SKB_FRAGS + 1];
+
+	/* The following fields are protected by event_lock.
+	 * vqs[VSOCK_VQ_EVENT] must be accessed with event_lock held.
+	 */
+	struct mutex event_lock;
+	bool event_run;
+	__dma_from_device_group_begin();
+	struct virtio_vsock_event event_list[8];
+	__dma_from_device_group_end();
 };
 
 static u32 virtio_transport_get_local_cid(void)
-- 
MST