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From:   kerneljasonxing@gmail.com
To:     jesse.brandeburg@intel.com, anthony.l.nguyen@intel.com,
        davem@davemloft.net, kuba@kernel.org, ast@kernel.org,
        daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com,
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Cc:     intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
        kerneljasonxing@gmail.com, Jason Xing <xingwanli@kuaishou.com>,
        Shujin Li <lishujin@kuaishou.com>
Subject: [PATCH] i40e: fix the panic when running bpf in xdpdrv mode
Date:   Mon, 12 Apr 2021 14:57:59 +0800
Message-Id: <20210412065759.2907-1-kerneljasonxing@gmail.com>
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From: Jason Xing <xingwanli@kuaishou.com>

Fix this by add more rules to calculate the value of @rss_size_max which
could be used in allocating the queues when bpf is loaded, which, however,
could cause the failure and then triger the NULL pointer of vsi->rx_rings.
Prio to this fix, the machine doesn't care about how many cpus are online
and then allocates 256 queues on the machine with 32 cpus online
actually.

Once the load of bpf begins, the log will go like this "failed to get
tracking for 256 queues for VSI 0 err -12" and this "setup of MAIN VSI
failed".

Thus, I attach the key information of the crash-log here.

BUG: unable to handle kernel NULL pointer dereference at
0000000000000000
RIP: 0010:i40e_xdp+0xdd/0x1b0 [i40e]
Call Trace:
[2160294.717292]  ? i40e_reconfig_rss_queues+0x170/0x170 [i40e]
[2160294.717666]  dev_xdp_install+0x4f/0x70
[2160294.718036]  dev_change_xdp_fd+0x11f/0x230
[2160294.718380]  ? dev_disable_lro+0xe0/0xe0
[2160294.718705]  do_setlink+0xac7/0xe70
[2160294.719035]  ? __nla_parse+0xed/0x120
[2160294.719365]  rtnl_newlink+0x73b/0x860

Signed-off-by: Jason Xing <xingwanli@kuaishou.com>
Signed-off-by: Shujin Li <lishujin@kuaishou.com>
---
 drivers/net/ethernet/intel/i40e/i40e_main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
index 521ea9d..4e9a247 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_main.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
@@ -11867,6 +11867,7 @@ static int i40e_sw_init(struct i40e_pf *pf)
 {
 	int err = 0;
 	int size;
+	u16 pow;
 
 	/* Set default capability flags */
 	pf->flags = I40E_FLAG_RX_CSUM_ENABLED |
@@ -11885,6 +11886,11 @@ static int i40e_sw_init(struct i40e_pf *pf)
 	pf->rss_table_size = pf->hw.func_caps.rss_table_size;
 	pf->rss_size_max = min_t(int, pf->rss_size_max,
 				 pf->hw.func_caps.num_tx_qp);
+
+	/* find the next higher power-of-2 of num cpus */
+	pow = roundup_pow_of_two(num_online_cpus());
+	pf->rss_size_max = min_t(int, pf->rss_size_max, pow);
+
 	if (pf->hw.func_caps.rss) {
 		pf->flags |= I40E_FLAG_RSS_ENABLED;
 		pf->alloc_rss_size = min_t(int, pf->rss_size_max,
-- 
1.8.3.1