linux-kernel - Re: [PATCH] mshv: hide x86-specific functions on arm64

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Message-ID: <20251216222129.GA1300707@liuwe-devbox-debian-v2.local>
Date: Tue, 16 Dec 2025 22:21:29 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
	Long Li <longli@...rosoft.com>,
	Stansialv Kinsburskii <skinsburskii@...ux.miscrosoft.com>,
	Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
	Praveen K Paladugu <prapal@...ux.microsoft.com>,
	Easwar Hariharan <easwar.hariharan@...ux.microsoft.com>,
	Anatol Belski <anbelski@...ux.microsoft.com>,
	Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>,
	Arnd Bergmann <arnd@...db.de>,
	Sean Christopherson <seanjc@...gle.com>,
	Naman Jain <namjain@...ux.microsoft.com>,
	linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mshv: hide x86-specific functions on arm64

On Tue, Dec 16, 2025 at 10:36:12PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The hv_sleep_notifiers_register() and hv_machine_power_off() functions are
> only called and declared on x86, but cause a warning on arm64:
> 
> drivers/hv/mshv_common.c:210:6: error: no previous prototype for 'hv_sleep_notifiers_register' [-Werror=missing-prototypes]
>   210 | void hv_sleep_notifiers_register(void)
>       |      ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/hv/mshv_common.c:224:6: error: no previous prototype for 'hv_machine_power_off' [-Werror=missing-prototypes]
>   224 | void hv_machine_power_off(void)
>       |      ^~~~~~~~~~~~~~~~~~~~
> 
> Hide both inside of an #ifdef block.
> 
> Fixes: f0be2600ac55 ("mshv: Use reboot notifier to configure sleep state")
> Fixes: 615a6e7d83f9 ("mshv: Cleanly shutdown root partition with MSHV")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks Arnd. I have a queued up a patch which make available the
declarations to arm64. Let me think about whether to use your patch
instead.

Anyway, this issue will be fixed one way or the other once I send a PR
to Linus.

Wei

> ---
>  drivers/hv/mshv_common.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/hv/mshv_common.c b/drivers/hv/mshv_common.c
> index 58027b23c206..63f09bb5136e 100644
> --- a/drivers/hv/mshv_common.c
> +++ b/drivers/hv/mshv_common.c
> @@ -142,6 +142,7 @@ int hv_call_get_partition_property(u64 partition_id,
>  }
>  EXPORT_SYMBOL_GPL(hv_call_get_partition_property);
>  
> +#ifdef CONFIG_X86
>  /*
>   * Corresponding sleep states have to be initialized in order for a subsequent
>   * HVCALL_ENTER_SLEEP_STATE call to succeed. Currently only S5 state as per
> @@ -237,3 +238,4 @@ void hv_machine_power_off(void)
>  	BUG();
>  
>  }
> +#endif
> -- 
> 2.39.5
>