[PATCH RFC 13/13] vsock/virtio: reorder fields to reduce struct padding

[Michael S. Tsirkin]

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=128:
- event_list is 32 bytes
- removing _end saves up to 128-32=96 bytes padding to align next field

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
 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_transport.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];
 
-	__dma_from_device_aligned_end
 	u32 guest_cid;
 	bool seqpacket_allow;
 
@@ -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];
 };
 
 static u32 virtio_transport_get_local_cid(void)
-- 
MST