Subject: Re: [PATCH] i40e: fix the panic when running bpf in xdpdrv mode

From: Jesse Brandeburg <[email-masked]>
Date: Mon, 12 Apr 2021 14:52:29 -0700

[email-masked] wrote:

> From: Jason Xing <[email-masked]>
> 
> Re: [PATCH] i40e: fix the panic when running bpf in xdpdrv mode

Please use netdev style subject lines when patching net kernel to
indicate which kernel tree this is targeted at, "net" or "net-next"
[PATCH net v2] i40e: ...

> Fix this by add more rules to calculate the value of @rss_size_max which

Fix this panic by adding ...

> 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.

trigger

> 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 <[email-masked]>
> Signed-off-by: Shujin Li <[email-masked]>

if you send to "net" - I suspect you should supply a Fixes: line, above
the sign-offs.
In this case however, this bug has been here since the beginning of the
driver, but the patch will easily apply, so please supply

Fixes: 41c445ff0f48 ("i40e: main driver core")

> ---
>  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);
> +

The fix itself is fine, and is correct as far as I can tell, thank you
for sending the patch!

>  	if (pf->hw.func_caps.rss) {
>  		pf->flags |= I40E_FLAG_RSS_ENABLED;
>  		pf->alloc_rss_size = min_t(int, pf->rss_size_max,