[PATCH net-next v3 4/4] gve: Default to max_rx_buffer_size for DQO if device supported

[joshwash@google.com]

From: Ankit Garg <nktgrg@google.com>

Change the driver's default behavior to prefer the largest available RX
buffer length supported by the device for DQO format, rather than always
using the hardcoded 2K default.

Previously, the driver would initialize with
`GVE_DEFAULT_RX_BUFFER_SIZE` (2K), even if the device advertised support
for a larger length (e.g., 4K).

Performance observations:
- With LRO disabled, we observed >10% improvement in RX single stream
throughput when MTU >=2048.
- With LRO enabled, we observed >10% improvement in RX single stream
throughput when MTU >=1460.
- No regressions were observed.

Signed-off-by: Ankit Garg <nktgrg@google.com>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Reviewed-by: Jordan Rhee <jordanrhee@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Joshua Washington <joshwash@google.com>
---
 drivers/net/ethernet/google/gve/gve_adminq.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/google/gve/gve_adminq.c b/drivers/net/ethernet/google/gve/gve_adminq.c
index 4f33d09..b72cc0f 100644
--- a/drivers/net/ethernet/google/gve/gve_adminq.c
+++ b/drivers/net/ethernet/google/gve/gve_adminq.c
@@ -987,6 +987,10 @@ static void gve_enable_supported_features(struct gve_priv *priv,
 		dev_info(&priv->pdev->dev,
 			 "BUFFER SIZES device option enabled with max_rx_buffer_size of %u, header_buf_size of %u.\n",
 			 priv->max_rx_buffer_size, priv->header_buf_size);
+		if (gve_is_dqo(priv) &&
+		    priv->max_rx_buffer_size > GVE_DEFAULT_RX_BUFFER_SIZE)
+			priv->rx_cfg.packet_buffer_size =
+				priv->max_rx_buffer_size;
 	}
 
 	/* Read and store ring size ranges given by device */
-- 
2.51.2.997.g839fc31de9-goog