netdev - [PATCH net-next] sfc: backport XDP EV queue sharing from the out-of-tree driver

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Message-ID: <CABWYdi0+PRk8h-Az=b3GqNDO=m6RZgqDL27tgwo3yMK_05OLAw@mail.gmail.com>
Date:   Thu, 10 Dec 2020 16:18:53 -0800
From:   Ivan Babrou <ivan@...udflare.com>
To:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Cc:     kernel-team <kernel-team@...udflare.com>,
        Edward Cree <ecree.xilinx@...il.com>,
        Martin Habets <habetsm.xilinx@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next] sfc: backport XDP EV queue sharing from the
 out-of-tree driver

Queue sharing behaviour already exists in the out-of-tree sfc driver,
available under xdp_alloc_tx_resources module parameter.

This avoids the following issue on machines with many cpus:

Insufficient resources for 12 XDP event queues (24 other channels, max 32)

Which in turn triggers EINVAL on XDP processing:

sfc 0000:86:00.0 ext0: XDP TX failed (-22)

Signed-off-by: Ivan Babrou <ivan@...udflare.com>
---
 drivers/net/ethernet/sfc/efx_channels.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/sfc/efx_channels.c
b/drivers/net/ethernet/sfc/efx_channels.c
index a4a626e9cd9a..1bfeee283ea9 100644
--- a/drivers/net/ethernet/sfc/efx_channels.c
+++ b/drivers/net/ethernet/sfc/efx_channels.c
@@ -17,6 +17,7 @@
 #include "rx_common.h"
 #include "nic.h"
 #include "sriov.h"
+#include "workarounds.h"

 /* This is the first interrupt mode to try out of:
  * 0 => MSI-X
@@ -137,6 +138,7 @@ static int efx_allocate_msix_channels(struct efx_nic *efx,
 {
  unsigned int n_channels = parallelism;
  int vec_count;
+ int tx_per_ev;
  int n_xdp_tx;
  int n_xdp_ev;

@@ -149,9 +151,9 @@ static int efx_allocate_msix_channels(struct efx_nic *efx,
  * multiple tx queues, assuming tx and ev queues are both
  * maximum size.
  */
-
+ tx_per_ev = EFX_MAX_EVQ_SIZE / EFX_TXQ_MAX_ENT(efx);
  n_xdp_tx = num_possible_cpus();
- n_xdp_ev = DIV_ROUND_UP(n_xdp_tx, EFX_MAX_TXQ_PER_CHANNEL);
+ n_xdp_ev = DIV_ROUND_UP(n_xdp_tx, tx_per_ev);

  vec_count = pci_msix_vec_count(efx->pci_dev);
  if (vec_count < 0)
--
2.29.2