linux-kernel - Re: [PATCH 1/3] wifi: ath11k: mark some QMI driver event helpers as noinline

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Message-ID: <87y11cx28u.fsf@kernel.org>
Date: Thu, 21 Nov 2024 13:20:01 +0200
From: Kalle Valo <kvalo@...nel.org>
To: Jeff Johnson <quic_jjohnson@...cinc.com>
Cc: Jeff Johnson <jjohnson@...nel.org>,  "Nathan Chancellor"
 <nathan@...nel.org>,  Nick Desaulniers <ndesaulniers@...gle.com>,  Bill
 Wendling <morbo@...gle.com>,  Justin Stitt <justinstitt@...gle.com>,
  "Arnd Bergmann" <arnd@...nel.org>,  <linux-wireless@...r.kernel.org>,
  <ath11k@...ts.infradead.org>,  <linux-kernel@...r.kernel.org>,
  <llvm@...ts.linux.dev>
Subject: Re: [PATCH 1/3] wifi: ath11k: mark some QMI driver event helpers as
 noinline

Jeff Johnson <quic_jjohnson@...cinc.com> writes:

> When compiling the ath11k driver using clang with KASAN enabled, the
> following warning is observed:
>
> drivers/net/wireless/ath/ath11k/qmi.c:3199:13: warning: stack frame size (1560) exceeds limit (1024) in 'ath11k_qmi_driver_event_work' [-Wframe-larger-than]
>
> This is similar to the issue found in ath12k/qmi.c that was discussed
> in [1] and fixed with [2]. The issue is that clang inlining can
> explode stack usage.
>
> Just as in ath12k, ath11k_qmi_driver_event_work() itself is a pretty
> lightweight function, but it dispatches to several other functions
> which do the real work:
>
> ath11k_qmi_driver_event_work()
> 	ath11k_qmi_event_server_arrive()
> 		ath11k_qmi_fw_ind_register_send()
> 		ath11k_qmi_host_cap_send() *
> 		ath11k_qmi_event_load_bdf()
> 	ath11k_qmi_event_mem_request()
> 		ath11k_qmi_respond_fw_mem_request()
> 	ath11k_qmi_event_load_bdf()
> 	ath11k_qmi_wlanfw_m3_info_send() *
> 		ath11k_qmi_m3_load()
> 	ath11k_qmi_process_coldboot_calibration()
>
> Of these, the two marked with * have non-trivial stack usage. Mark
> those functions as 'noinline_for_stack' to prevent them from being
> inlined in ath12k_qmi_driver_event_work(), thereby eliminating the
> excessive stack usage.
>
> Note that this approach is a bit more "surgical" than the ath12k
> approach as only the two functions with the largest stack usage are
> modified.
>
> Link: https://msgid.link/bc214795-1c51-4cb7-922f-67d6ef98bff2@quicinc.com # [1]
> Link: https://patch.msgid.link/20241028-ath12k_qmi_driver_event_work-v1-1-0d532eb593fa@quicinc.com # [2]
> Signed-off-by: Jeff Johnson <quic_jjohnson@...cinc.com>

Acked-by: Kalle Valo <kvalo@...nel.org>

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