netdev - [PATCH] net-af_xdp: use correct number of channels from ethtool

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Message-Id: <20191118225523.41697-1-lrizzo@google.com>
Date:   Mon, 18 Nov 2019 14:55:23 -0800
From:   Luigi Rizzo <lrizzo@...gle.com>
To:     magnus.karlsson@...el.com, bjorn.topel@...el.com,
        jonathan.lemon@...il.com, netdev@...r.kernel.org
Cc:     bpf@...r.kernel.org, rizzo@....unipi.it,
        Luigi Rizzo <lrizzo@...gle.com>
Subject: [PATCH] net-af_xdp: use correct number of channels from ethtool

Drivers use different fields to report the number of channels, so take
the maximum of all fields (rx, tx, other, combined) when determining the
size of the xsk map. The current code used only 'combined' which was set
to 0 in some drivers e.g. mlx4.

Tested: compiled and run xdpsock -q 3 -r -S on mlx4
Signed-off-by: Luigi Rizzo <lrizzo@...gle.com>
---
 tools/lib/bpf/xsk.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index 74d84f36a5b24..8e12269428d08 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -412,6 +412,11 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
 	return 0;
 }
 
+static inline int max_i(int a, int b)
+{
+	return a > b ? a : b;
+}
+
 static int xsk_get_max_queues(struct xsk_socket *xsk)
 {
 	struct ethtool_channels channels = { .cmd = ETHTOOL_GCHANNELS };
@@ -431,13 +436,18 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
 		goto out;
 	}
 
-	if (err || channels.max_combined == 0)
+	if (err) {
 		/* If the device says it has no channels, then all traffic
 		 * is sent to a single stream, so max queues = 1.
 		 */
 		ret = 1;
-	else
-		ret = channels.max_combined;
+	} else {
+		/* Take the max of rx, tx, other, combined. Drivers return
+		 * the number of channels in different ways.
+		 */
+		ret = max_i(max_i(channels.max_rx, channels.max_tx),
+			      max_i(channels.max_other, channels.max_combined));
+	}
 
 out:
 	close(fd);
-- 
2.24.0.432.g9d3f5f5b63-goog