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

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Message-ID: <zlzpmburt4o75yizy6uknx4ews4eox6wbr5jleuixp6o6v2tuk@sz6k4x4gcolo>
Date: Thu, 12 Jun 2025 11:01:03 +0100
From: Pedro Falcato <pfalcato@...e.de>
To: Baochen Qiang <quic_bqiang@...cinc.com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, 
	akpm@...ux-foundation.org, Jeff Johnson <jjohnson@...nel.org>, 
	linux-wireless@...r.kernel.org, ath11k@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org
Subject: Re: [PATCHv2] wifi: ath11k: mark reset srng lists as uninitialized

On Thu, Jun 12, 2025 at 04:01:49PM +0800, Baochen Qiang wrote:
> [+ 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.
> 

Any memory that is virtually-mapped (read: vmalloc, vmap, vm_map_ram, and others)
will be unmapped on its subsequent free. I'm not familiar with the DMA subsystem,
but the address ffffb4e4c046f010 is vmalloc-like.

> 
> > <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
> 

-- 
Pedro