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

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Message-ID: <aUH9GGzROHfbP6pj@skinsburskii.localdomain>
Date: Tue, 16 Dec 2025 16:45:12 -0800
From: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
To: Wei Liu <wei.liu@...nel.org>
Cc: Arnd Bergmann <arnd@...nel.org>, "K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	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>,
	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 10:21:29PM +0000, Wei Liu wrote:
> 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.
> 

The whole idea of mshv_common.c is to have common code for all archs.
It would be nice to keep this file as it is.

Thanks,
Stanislav

> 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
> >