linux-kernel - Re: [PATCH v2 1/3] bus: mhi: host: keep bhi buffer through suspend cycle

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Message-ID: <2025071604-scandal-outpost-eb22@gregkh>
Date: Wed, 16 Jul 2025 11:34:37 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc: Manivannan Sadhasivam <mani@...nel.org>,
	Jeff Hugo <jeff.hugo@....qualcomm.com>,
	Youssef Samir <quic_yabdulra@...cinc.com>,
	Matthew Leung <quic_mattleun@...cinc.com>,
	Alexander Wilhelm <alexander.wilhelm@...termo.com>,
	Kunwu Chan <chentao@...inos.cn>,
	Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
	Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>,
	Yan Zhen <yanzhen@...o.com>, Sujeev Dias <sdias@...eaurora.org>,
	Siddartha Mohanadoss <smohanad@...eaurora.org>, mhi@...ts.linux.dev,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...labora.com, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/3] bus: mhi: host: keep bhi buffer through suspend
 cycle

On Tue, Jul 15, 2025 at 06:25:07PM +0500, Muhammad Usama Anjum wrote:
> When there is memory pressure, at resume time dma_alloc_coherent()
> returns error which in turn fails the loading of firmware and hence
> the driver crashes:
> 
> kernel: kworker/u33:5: page allocation failure: order:7,
> mode:0xc04(GFP_NOIO|GFP_DMA32), nodemask=(null),cpuset=/,mems_allowed=0
> kernel: CPU: 1 UID: 0 PID: 7693 Comm: kworker/u33:5 Not tainted 6.11.11-valve17-1-neptune-611-g027868a0ac03 #1 3843143b92e9da0fa2d3d5f21f51beaed15c7d59
> kernel: Hardware name: Valve Galileo/Galileo, BIOS F7G0112 08/01/2024
> kernel: Workqueue: mhi_hiprio_wq mhi_pm_st_worker [mhi]
> kernel: Call Trace:
> kernel:  <TASK>
> kernel:  dump_stack_lvl+0x4e/0x70
> kernel:  warn_alloc+0x164/0x190
> kernel:  ? srso_return_thunk+0x5/0x5f
> kernel:  ? __alloc_pages_direct_compact+0xaf/0x360
> kernel:  __alloc_pages_slowpath.constprop.0+0xc75/0xd70
> kernel:  __alloc_pages_noprof+0x321/0x350
> kernel:  __dma_direct_alloc_pages.isra.0+0x14a/0x290
> kernel:  dma_direct_alloc+0x70/0x270
> kernel:  mhi_fw_load_handler+0x126/0x340 [mhi a96cb91daba500cc77f86bad60c1f332dc3babdf]
> kernel:  mhi_pm_st_worker+0x5e8/0xac0 [mhi a96cb91daba500cc77f86bad60c1f332dc3babdf]
> kernel:  ? srso_return_thunk+0x5/0x5f
> kernel:  process_one_work+0x17e/0x330
> kernel:  worker_thread+0x2ce/0x3f0
> kernel:  ? __pfx_worker_thread+0x10/0x10
> kernel:  kthread+0xd2/0x100
> kernel:  ? __pfx_kthread+0x10/0x10
> kernel:  ret_from_fork+0x34/0x50
> kernel:  ? __pfx_kthread+0x10/0x10
> kernel:  ret_from_fork_asm+0x1a/0x30
> kernel:  </TASK>
> kernel: Mem-Info:
> kernel: active_anon:513809 inactive_anon:152 isolated_anon:0
>     active_file:359315 inactive_file:2487001 isolated_file:0
>     unevictable:637 dirty:19 writeback:0
>     slab_reclaimable:160391 slab_unreclaimable:39729
>     mapped:175836 shmem:51039 pagetables:4415
>     sec_pagetables:0 bounce:0
>     kernel_misc_reclaimable:0
>     free:125666 free_pcp:0 free_cma:0

This is not a "crash", it is a warning that your huge memory allocation
did not succeed.  Properly handle this issue (and if you know it's going
to happen, turn the warning off in your allocation), and you should be
fine.

> In above example, if we sum all the consumed memory, it comes out
> to be 15.5GB and free memory is ~ 500MB from a total of 16GB RAM.
> Even though memory is present. But all of the dma memory has been
> exhausted or fragmented.

What caused that to happen?

> Fix it by allocating it only once and then reuse the same allocated
> memory. As we'll allocate this memory only once, this memory will stay
> allocated.

As others said, no, don't consume memory for no good reason, that just
means that other devices will fail more frequently.  If all
devices/drivers did this, you wouldn't have memory to work either.

thanks,

greg k-h