netdev - [PATCH bpf-next v4 07/17] libbpf: Support drivers with non-combined channels

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Date:   Wed, 12 Jun 2019 15:56:48 +0000
From:   Maxim Mikityanskiy <maximmi@...lanox.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>
CC:     "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jonathan Lemon <bsd@...com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Maciej Fijalkowski <maciejromanfijalkowski@...il.com>,
        Maxim Mikityanskiy <maximmi@...lanox.com>
Subject: [PATCH bpf-next v4 07/17] libbpf: Support drivers with non-combined
 channels

Currently, libbpf uses the number of combined channels as the maximum
queue number. However, the kernel has a different limitation:

- xdp_reg_umem_at_qid() allows up to max(RX queues, TX queues).

- ethtool_set_channels() checks for UMEMs in queues up to
  combined_count + max(rx_count, tx_count).

libbpf shouldn't limit applications to a lower max queue number. Account
for non-combined RX and TX channels when calculating the max queue
number. Use the same formula that is used in ethtool.

Signed-off-by: Maxim Mikityanskiy <maximmi@...lanox.com>
Reviewed-by: Tariq Toukan <tariqt@...lanox.com>
Acked-by: Saeed Mahameed <saeedm@...lanox.com>
---
 tools/lib/bpf/xsk.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index bf15a80a37c2..86107857e1f0 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -334,13 +334,13 @@ static int xsk_get_max_queues(struct xsk_socket *xsk)
 		goto out;
 	}
 
-	if (channels.max_combined == 0 || errno == EOPNOTSUPP)
+	ret = channels.max_combined + max(channels.max_rx, channels.max_tx);
+
+	if (ret == 0 || errno == EOPNOTSUPP)
 		/* 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;
 
 out:
 	close(fd);
-- 
2.19.1