Re: [PATCHv2] wifi: ath11k: mark reset srng lists as uninitialized

[Baochen Qiang <quic_bqiang@quicinc.com>]

[+ kernel mm list]

On 6/12/2025 1:04 PM, Sergey Senozhatsky wrote:
> On (25/06/12 11:30), Baochen Qiang wrote:
>> On 5/29/2025 11:56 AM, Sergey Senozhatsky wrote:
>>> ath11k_hal_srng_deinit() frees rdp and wrp which are used
>>> by srng lists.  Mark srng lists as not-initialized.  This
>>> makes sense, for instance, when device fails to resume
>>> and the driver calls ath11k_hal_srng_deinit() from
>>> ath11k_core_reconfigure_on_crash().
>>
>> Did you see any issue without your change?
> 
> We do see some issues, yes, on LTS kernels.
> 
> [..]
>>> diff --git a/drivers/net/wireless/ath/ath11k/hal.c b/drivers/net/wireless/ath/ath11k/hal.c
>>> index 8cb1505a5a0c..cab11a35f911 100644
>>> --- a/drivers/net/wireless/ath/ath11k/hal.c
>>> +++ b/drivers/net/wireless/ath/ath11k/hal.c
>>> @@ -1346,6 +1346,10 @@ EXPORT_SYMBOL(ath11k_hal_srng_init);
>>>  void ath11k_hal_srng_deinit(struct ath11k_base *ab)
>>>  {
>>>  	struct ath11k_hal *hal = &ab->hal;
>>> +	int i;
>>> +
>>> +	for (i = 0; i < HAL_SRNG_RING_ID_MAX; i++)
>>> +		ab->hal.srng_list[i].initialized = 0;
>>
>> With this flag reset, srng stats would not be dumped in ath11k_hal_dump_srng_stats().
> 
> I think un-initialized lists should not be dumped.
> 
> ath11k_hal_srng_deinit() releases wrp.vaddr and rdp.vaddr, which are
> accessed, as far as I understand it, in ath11k_hal_dump_srng_stats()
> as *srng->u.src_ring.tp_addr and *srng->u.dst_ring.hp_addr, presumably,
> causing things like:
> 
> <1>[173154.396775] BUG: unable to handle page fault for address: ffffb4e4c046f010
> <1>[173154.396778] #PF: supervisor read access in kernel mode
> <1>[173154.396781] #PF: error_code(0x0000) - not-present page

I am confused here: if the root cause is driver trying to read a freed memory, it should
not result in a PF issue. Because even if freed, the page is there and still mapped in
kernel page table.

Andrew, any insights?

> <4>[173154.396824] RIP: 0010:ath11k_hal_dump_srng_stats+0x2b4/0x3b0 [ath11k]
> <4>[173154.396839] Code: 88 c0 44 89 f2 89 c1 e8 3a 14 06 00 41 be e8 25 00 00 eb 6e 42 0f b6 84 33 78 ff ff ff 89 45 d0 46 8b 7c 33 d8 4a 8b 44 33 e0 <44> 8b 20 46 8b 6c 33 e8 42 8b 04 33 48 89 45 c8 48 8b 3d 45 a3 a0
> <4>[173154.396842] RSP: 0018:ffffb4e4dceefc50 EFLAGS: 00010246
> <4>[173154.396846] RAX: ffffb4e4c046f010 RBX: ffff90d1c3040000 RCX: a0009634a5d28c00
> <4>[173154.396849] RDX: ffffffffb0279d80 RSI: ffffffffb0279d80 RDI: ffff90d2e5d17488
> <4>[173154.396851] RBP: ffffb4e4dceefc90 R08: ffffffffb0249d80 R09: 0000000000003b82
> <4>[173154.396854] R10: 0000000000000004 R11: 00000000ffffffea R12: ffff90d1c3041c90
> <4>[173154.396856] R13: ffff90d1c3040000 R14: 0000000000002828 R15: 0000000000000000
> <4>[173154.396859] FS: 0000000000000000(0000) GS:ffff90d2e5d00000(0000) knlGS:0000000000000000
> <4>[173154.396862] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> <4>[173154.396865] CR2: ffffb4e4c046f010 CR3: 000000005ca24000 CR4: 0000000000750ee0
> <4>[173154.396868] PKRU: 55555554
> <4>[173154.396870] Call Trace:
> <4>[173154.396874] <TASK>
> <4>[173154.396883] ? __die_body+0xae/0xb0
> <4>[173154.396890] ? page_fault_oops+0x381/0x3e0
> <4>[173154.396896] ? exc_page_fault+0x69/0xa0
> <4>[173154.396901] ? asm_exc_page_fault+0x22/0x30
> <4>[173154.396908] ? ath11k_hal_dump_srng_stats+0x2b4/0x3b0 [ath11k (HASH:3de7 4)]
> <4>[173154.396923] ath11k_qmi_driver_event_work+0xbd/0x1050 [ath11k (HASH:3de7 4)]
> <4>[173154.396942] worker_thread+0x390/0x960
> <4>[173154.396949] kthread+0x149/0x170