linux-kernel - Re: [PATCH] i40e: fix the panic when running bpf in xdpdrv mode

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Date:   Tue, 13 Apr 2021 10:17:00 +0800
From:   Jason Xing <kerneljasonxing@...il.com>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc:     anthony.l.nguyen@...el.com, David Miller <davem@...emloft.net>,
        kuba@...nel.org, ast@...nel.org, daniel@...earbox.net,
        hawk@...nel.org, john.fastabend@...il.com, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        kpsingh@...nel.org, intel-wired-lan@...ts.osuosl.org,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, bpf@...r.kernel.org,
        Jason Xing <xingwanli@...ishou.com>,
        Shujin Li <lishujin@...ishou.com>
Subject: Re: [PATCH] i40e: fix the panic when running bpf in xdpdrv mode

On Tue, Apr 13, 2021 at 5:52 AM Jesse Brandeburg
<jesse.brandeburg@...el.com> wrote:
>
> kerneljasonxing@...il.com wrote:
>
> > From: Jason Xing <xingwanli@...ishou.com>
> >
> > 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 <xingwanli@...ishou.com>
> > Signed-off-by: Shujin Li <lishujin@...ishou.com>
>
> 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!
>

Thanks for your advice. I'm going to send the patch v2 :)

Jason

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