netdev - Re: [PATCH v3 net 2/2] net: enetc: Do not configure preemptible TCs if SIs do not support

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Message-ID: <Z0S3CEYeGSWLPKVh@lizhi-Precision-Tower-5810>
Date: Mon, 25 Nov 2024 12:42:32 -0500
From: Frank Li <Frank.li@....com>
To: Wei Fang <wei.fang@....com>
Cc: claudiu.manoil@....com, vladimir.oltean@....com, xiaoning.wang@....com,
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev
Subject: Re: [PATCH v3 net 2/2] net: enetc: Do not configure preemptible TCs
 if SIs do not support

On Mon, Nov 25, 2024 at 05:07:19PM +0800, Wei Fang wrote:
> Both ENETC PF and VF drivers share enetc_setup_tc_mqprio() to configure
> MQPRIO. And enetc_setup_tc_mqprio() calls enetc_change_preemptible_tcs()
> to configure preemptible TCs. However, only PF is able to configure
> preemptible TCs. Because only PF has related registers, while VF does not
> have these registers. So for VF, its hw->port pointer is NULL. Therefore,
> VF will access an invalid pointer when accessing a non-existent register,
> which will cause a crash issue. The simplified log is as follows.
>
> root@...028ardb:~# tc qdisc add dev eno0vf0 parent root handle 100: \
> mqprio num_tc 4 map 0 0 1 1 2 2 3 3 queues 1@0 1@1 1@2 1@3 hw 1
> [  187.290775] Unable to handle kernel paging request at virtual address 0000000000001f00
> [  187.424831] pc : enetc_mm_commit_preemptible_tcs+0x1c4/0x400
> [  187.430518] lr : enetc_mm_commit_preemptible_tcs+0x30c/0x400
> [  187.511140] Call trace:
> [  187.513588]  enetc_mm_commit_preemptible_tcs+0x1c4/0x400
> [  187.518918]  enetc_setup_tc_mqprio+0x180/0x214
> [  187.523374]  enetc_vf_setup_tc+0x1c/0x30
> [  187.527306]  mqprio_enable_offload+0x144/0x178
> [  187.531766]  mqprio_init+0x3ec/0x668
> [  187.535351]  qdisc_create+0x15c/0x488
> [  187.539023]  tc_modify_qdisc+0x398/0x73c
> [  187.542958]  rtnetlink_rcv_msg+0x128/0x378
> [  187.547064]  netlink_rcv_skb+0x60/0x130
> [  187.550910]  rtnetlink_rcv+0x18/0x24
> [  187.554492]  netlink_unicast+0x300/0x36c
> [  187.558425]  netlink_sendmsg+0x1a8/0x420
> [  187.606759] ---[ end trace 0000000000000000 ]---
>
> In addition, some PFs also do not support configuring preemptible TCs,
> such as eno1 and eno3 on LS1028A. It won't crash like it does for VFs,
> but we should prevent these PFs from accessing these unimplemented
> registers.
>
> Fixes: 827145392a4a ("net: enetc: only commit preemptible TCs to hardware when MM TX is active")
> Signed-off-by: Wei Fang <wei.fang@....com>
> Suggested-by: Vladimir Oltean <vladimir.oltean@....com>

Reviewed-by: Frank Li <Frank.Li@....com>
> ---
> v2 changes:
> 1. Change the title and refine the commit message
> 2. Only set ENETC_SI_F_QBU bit for PFs which support Qbu
> 3. Prevent all SIs which not support Qbu from configuring preemptible
> TCs
> v3 changes:
> 1. remove the changes in enetc_get_si_caps().
> ---
>  drivers/net/ethernet/freescale/enetc/enetc.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
> index bece220535a1..535969fa0fdb 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> @@ -29,6 +29,9 @@ EXPORT_SYMBOL_GPL(enetc_port_mac_wr);
>  static void enetc_change_preemptible_tcs(struct enetc_ndev_priv *priv,
>  					 u8 preemptible_tcs)
>  {
> +	if (!(priv->si->hw_features & ENETC_SI_F_QBU))
> +		return;
> +
>  	priv->preemptible_tcs = preemptible_tcs;
>  	enetc_mm_commit_preemptible_tcs(priv);
>  }
> --
> 2.34.1
>