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.
This is due to the fact that the value we use (rxq->id) is not the per-port queue index which
XDP expects -- it's a global index which should not be used in this case. Instead we shall use
rxq->logic_rxq which is the correct, per-port value.
Signed-off-by: Louis Amas <louis.amas@xxxxxxxx>
Signed-off-by: Emmanuel Deloget <emmanuel.deloget@xxxxxxxx>
---
As we were trying to capture packets using XDP on our mv8040-powered
MacchiatoBin, we experienced an issue related to rx queue numbering.
Before I get to the problem itself, a bit of setup:
* the Macchiato has several ports, all of them handled using the mvpp2
ethernet driver. We are able to reproduce our issue on any device whose
port->id != 0 (we used eth2 for our tests). When port->id == 0 (for
example on eth0) everything works as expected ;
* we use xdp-tutorial for our tests ; more specifically, we used the
advanced03-AF_XDP tutorial as it provides a simple testbed. We modified
the kernel to simplify it:
SEC("xdp_sock")
int xdp_sock_prog(struct xdp_md *ctx)
{
int index = ctx->rx_queue_index;
/* A set entry here means that the correspnding queue_id
* has an active AF_XDP socket bound to it. */
if (bpf_map_lookup_elem(&xsks_map, &index))
return bpf_redirect_map(&xsks_map, index, 0);
return XDP_PASS;
}
* we tested kernel 5.10 (out target) and 5.15 (for reference) ; both kernels
exhibits the same symptoms ; I expect kernel 5.9 (the first linux kernel
with XDP support in the mvpp2 driver) to exhibit the same problem.
The normal invocation of this program would be:
./af_xdp_user -d ETHDEV
We should then capture packets on this interface. When ETHDEV is eth0
(port->id == 0) everything works as expcted ; when using ETHDEV == eth2
we fail to capture anything.
We investigated the issue and found that XDP rx queues (setup as
struct xdp_rxq_info by the mvpp2 driver) for this device were wrong. XDP
expected them to be numbered in [0..3] but we found numbers in [32..35].
The reason for this lies in mvpp2_main.c at lines 2962 and 2966 which are
of the form (symbolic notation, close to actual code, function
mvpp2_rxq_init()):
err = xdp_rxq_info_reg(&rxq->some_xdp_rxqinfo, port->dev, rxq->id, 0);
The rxq->id value we pass to this function is incorrect - it's a virtual queue
id which is computed as (symbolic notation, not actual code):
rxq->id = port->id * max_rxq_count + queue_id
In our case, max_rxq_count == 32 and port->id == 1 for eth2, meaning our
rxq->id are in the range [32..35] (for 4 queues).
We tried to force the rx queue id on the XDP side by using:
./af_xdp_user -d eth2 -Q 32
But that failed -- as expected, because we should not have more than 4
rx queues.
The computing of rxq->id is valid, but the use of rxq->id in this context is
not. What we really want here is the rx queue id for this port, and this value
is stored in rxq->logic_rxq -- as hinted by the code in mvpp2_rxq_init().
Replacing rxq->id by this value in the two xdp_rxq_info_reg() calls fixed the
issue and allowed us to use XDP on all the Macchiato ethernet ports.
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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