Re: [PATCH net 3/3] net: libwx: properly reset Rx ring descriptor

[Simon Horman <horms@kernel.org>]

On Wed, Jul 09, 2025 at 02:40:25PM +0800, Jiawen Wu wrote:
> When device reset is triggered by feature changes such as toggling Rx
> VLAN offload, wx->do_reset() is called to reinitialize Rx rings. The
> hardware descriptor ring may retain stale values from previous sessions.
> And only set the length to 0 in rx_desc[0] would result in building
> malformed SKBs. Fix it to ensure a clean slate after device reset.
> 
> [  549.186435] [     C16] ------------[ cut here ]------------
> [  549.186457] [     C16] kernel BUG at net/core/skbuff.c:2814!
> [  549.186468] [     C16] Oops: invalid opcode: 0000 [#1] SMP NOPTI
> [  549.186472] [     C16] CPU: 16 UID: 0 PID: 0 Comm: swapper/16 Kdump: loaded Not tainted 6.16.0-rc4+ #23 PREEMPT(voluntary)
> [  549.186476] [     C16] Hardware name: Micro-Star International Co., Ltd. MS-7E16/X670E GAMING PLUS WIFI (MS-7E16), BIOS 1.90 12/31/2024
> [  549.186478] [     C16] RIP: 0010:__pskb_pull_tail+0x3ff/0x510
> [  549.186484] [     C16] Code: 06 f0 ff 4f 34 74 7b 4d 8b 8c 24 c8 00 00 00 45 8b 84 24 c0 00 00 00 e9 c8 fd ff ff 48 c7 44 24 08 00 00 00 00 e9 5e fe ff ff <0f> 0b 31 c0 e9 23 90 5b ff 41 f7 c6 ff 0f 00 00 75 bf 49 8b 06 a8
> [  549.186487] [     C16] RSP: 0018:ffffb391c0640d70 EFLAGS: 00010282
> [  549.186490] [     C16] RAX: 00000000fffffff2 RBX: ffff8fe7e4d40200 RCX: 00000000fffffff2
> [  549.186492] [     C16] RDX: ffff8fe7c3a4bf8e RSI: 0000000000000180 RDI: ffff8fe7c3a4bf40
> [  549.186494] [     C16] RBP: ffffb391c0640da8 R08: ffff8fe7c3a4c0c0 R09: 000000000000000e
> [  549.186496] [     C16] R10: ffffb391c0640d88 R11: 000000000000000e R12: ffff8fe7e4d40200
> [  549.186497] [     C16] R13: 00000000fffffff2 R14: ffff8fe7fa01a000 R15: 00000000fffffff2
> [  549.186499] [     C16] FS:  0000000000000000(0000) GS:ffff8fef5ae40000(0000) knlGS:0000000000000000
> [  549.186502] [     C16] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  549.186503] [     C16] CR2: 00007f77d81d6000 CR3: 000000051a032000 CR4: 0000000000750ef0
> [  549.186505] [     C16] PKRU: 55555554
> [  549.186507] [     C16] Call Trace:
> [  549.186510] [     C16]  <IRQ>
> [  549.186513] [     C16]  ? srso_alias_return_thunk+0x5/0xfbef5
> [  549.186517] [     C16]  __skb_pad+0xc7/0xf0
> [  549.186523] [     C16]  wx_clean_rx_irq+0x355/0x3b0 [libwx]
> [  549.186533] [     C16]  wx_poll+0x92/0x120 [libwx]
> [  549.186540] [     C16]  __napi_poll+0x28/0x190
> [  549.186544] [     C16]  net_rx_action+0x301/0x3f0
> [  549.186548] [     C16]  ? srso_alias_return_thunk+0x5/0xfbef5
> [  549.186551] [     C16]  ? __raw_spin_lock_irqsave+0x1e/0x50
> [  549.186554] [     C16]  ? srso_alias_return_thunk+0x5/0xfbef5
> [  549.186557] [     C16]  ? wake_up_nohz_cpu+0x35/0x160
> [  549.186559] [     C16]  ? srso_alias_return_thunk+0x5/0xfbef5
> [  549.186563] [     C16]  handle_softirqs+0xf9/0x2c0
> [  549.186568] [     C16]  __irq_exit_rcu+0xc7/0x130
> [  549.186572] [     C16]  common_interrupt+0xb8/0xd0
> [  549.186576] [     C16]  </IRQ>
> [  549.186577] [     C16]  <TASK>
> [  549.186579] [     C16]  asm_common_interrupt+0x22/0x40
> [  549.186582] [     C16] RIP: 0010:cpuidle_enter_state+0xc2/0x420
> [  549.186585] [     C16] Code: 00 00 e8 11 0e 5e ff e8 ac f0 ff ff 49 89 c5 0f 1f 44 00 00 31 ff e8 0d ed 5c ff 45 84 ff 0f 85 40 02 00 00 fb 0f 1f 44 00 00 <45> 85 f6 0f 88 84 01 00 00 49 63 d6 48 8d 04 52 48 8d 04 82 49 8d
> [  549.186587] [     C16] RSP: 0018:ffffb391c0277e78 EFLAGS: 00000246
> [  549.186590] [     C16] RAX: ffff8fef5ae40000 RBX: 0000000000000003 RCX: 0000000000000000
> [  549.186591] [     C16] RDX: 0000007fde0faac5 RSI: ffffffff826e53f6 RDI: ffffffff826fa9b3
> [  549.186593] [     C16] RBP: ffff8fe7c3a20800 R08: 0000000000000002 R09: 0000000000000000
> [  549.186595] [     C16] R10: 0000000000000000 R11: 000000000000ffff R12: ffffffff82ed7a40
> [  549.186596] [     C16] R13: 0000007fde0faac5 R14: 0000000000000003 R15: 0000000000000000
> [  549.186601] [     C16]  ? cpuidle_enter_state+0xb3/0x420
> [  549.186605] [     C16]  cpuidle_enter+0x29/0x40
> [  549.186609] [     C16]  cpuidle_idle_call+0xfd/0x170
> [  549.186613] [     C16]  do_idle+0x7a/0xc0
> [  549.186616] [     C16]  cpu_startup_entry+0x25/0x30
> [  549.186618] [     C16]  start_secondary+0x117/0x140
> [  549.186623] [     C16]  common_startup_64+0x13e/0x148
> [  549.186628] [     C16]  </TASK>
> 
> Fixes: 3c47e8ae113a ("net: libwx: Support to receive packets in NAPI")
> Cc: stable@vger.kernel.org
> Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>

Reviewed-by: Simon Horman <horms@kernel.org>

> diff --git a/drivers/net/ethernet/wangxun/libwx/wx_hw.c b/drivers/net/ethernet/wangxun/libwx/wx_hw.c

...

> @@ -1942,9 +1941,9 @@ static void wx_configure_rx_ring(struct wx *wx,
>  	memset(ring->rx_buffer_info, 0,
>  	       sizeof(struct wx_rx_buffer) * ring->count);
>  
> -	/* initialize Rx descriptor 0 */
> -	rx_desc = WX_RX_DESC(ring, 0);
> -	rx_desc->wb.upper.length = 0;
> +	/* reset ntu and ntc to place SW in sync with hardwdare */

nit: hardware

...