netdev - [PATCH 1/1] net: mvpp2: fix XDP rx queues registering

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Message-Id: <20211110144104.241589-1-louis.amas@eho.link>
Date:   Wed, 10 Nov 2021 15:41:06 +0100
From:   Louis Amas <louis.amas@....link>
To:     emmanuel.deloget@....link
Cc:     andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
        daniel@...earbox.net, davem@...emloft.net, hawk@...nel.org,
        john.fastabend@...il.com, kafai@...com, kpsingh@...nel.org,
        kuba@...nel.org, linux-kernel@...r.kernel.org,
        linux@...linux.org.uk, louis.amas@....link, mw@...ihalf.com,
        netdev@...r.kernel.org, songliubraving@...com, yhs@...com
Subject: [PATCH 1/1] net: mvpp2: fix XDP rx queues registering

The registration of XDP queue information is incorrect because the
RX queue id we use is invalid. When port->id == 0 it appears to works
as expected yet it's no longer the case when port->id != 0.

When we register the XDP rx queue information (using
xdp_rxq_info_reg() in function mvpp2_rxq_init()) we tell them to use
rxq->id as the queue id. This value iscomputed as:
rxq->id = port->id * max_rxq_count + queue_id

where max_rxq_count depends on the device version. In the MB case,
this value is 32, meaning that rx queues on eth2 are numbered from
32 to 35 - there are four of them.

Clearly, this is not the per-port queue id that XDP is expecting:
it wants a value in the range [0..3]. It shall directly use queue_id
which is stored in rxq->logic_rxq -- so let's use that value instead.

This is consistent with the remaining part of the code in
mvpp2_rxq_init().

Fixes: b27db2274ba8 ("mvpp2: use page_pool allocator")
Signed-off-by: Louis Amas <louis.amas@....link>
Signed-off-by: Emmanuel Deloget <emmanuel.deloget@....link>
Reviewed-by: Marcin Wojtas <mw@...ihalf.com>
---
This is a repost of [1]. The patch itself is not changed, but the
commit message has been enhanced using part of the explaination in
order to make it clearer (hopefully) and to incorporate the
reviewed-by tag from Marcin.

v1: original patch
v2: revamped commit description (no change in the patch itself)

[1] https://lore.kernel.org/bpf/20211109103101.92382-1-louis.amas@eho.link/

 drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
index 587def69a6f7..f0ea377341c6 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -2959,11 +2959,11 @@ static int mvpp2_rxq_init(struct mvpp2_port *port,
        mvpp2_rxq_status_update(port, rxq->id, 0, rxq->size);

        if (priv->percpu_pools) {
-               err = xdp_rxq_info_reg(&rxq->xdp_rxq_short, port->dev, rxq->id, 0);
+               err = xdp_rxq_info_reg(&rxq->xdp_rxq_short, port->dev, rxq->logic_rxq, 0);
                if (err < 0)
                        goto err_free_dma;

-               err = xdp_rxq_info_reg(&rxq->xdp_rxq_long, port->dev, rxq->id, 0);
+               err = xdp_rxq_info_reg(&rxq->xdp_rxq_long, port->dev, rxq->logic_rxq, 0);
                if (err < 0)
                        goto err_unregister_rxq_short;

--
2.25.1


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