RE: [tip:x86/hyperv] x86/Hyper-V/hv_apic: Build the Hyper-V APIC conditionally

[KY Srinivasan]

> -----Original Message-----
> From: tip tree robot <tipbot@xxxxxxxxx>
> Sent: Saturday, May 19, 2018 12:40 PM
> To: linux-tip-commits@xxxxxxxxxxxxxxx
> Cc: lkp@xxxxxxxxx; hpa@xxxxxxxxx; mingo@xxxxxxxxxx; Michael Kelley
> (EOSG) <Michael.H.Kelley@xxxxxxxxxxxxx>; tglx@xxxxxxxxxxxxx; KY
> Srinivasan <kys@xxxxxxxxxxxxx>
> Subject: [tip:x86/hyperv] x86/Hyper-V/hv_apic: Build the Hyper-V APIC
> conditionally
> 
> Commit-ID:  2d2ccf24939cf369f7473c7e4ea309891be91848
> Gitweb:
> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.ker
> nel.org%2Ftip%2F2d2ccf24939cf369f7473c7e4ea309891be91848&data=02%7C
> 01%7Ckys%40microsoft.com%7C4ca32d3abd084c7a96b608d5bdc04fd9%7C72
> f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636623556042008674&sdata
> =F04rsVvpkPMwuzsQF6odQX2jER84S4AYcVQr4CB0yc0%3D&reserved=0
> Author:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> AuthorDate: Sat, 19 May 2018 21:22:48 +0200
> Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> CommitDate: Sat, 19 May 2018 21:34:11 +0200
> 
> x86/Hyper-V/hv_apic: Build the Hyper-V APIC conditionally
> 
> The Hyper-V APIC code is built when CONFIG_HYPERV is enabled but the
> actual
> code in that file is guarded with CONFIG_X86_64. There is no point in doing
> this. Neither is there a point in having the CONFIG_HYPERV guard in there
> because the containing directory is not built when CONFIG_HYPERV=n.
> 
> Further for the hv_init_apic() function a stub is provided only for
> CONFIG_HYPERV=n, which is pointless as the callsite is not compiled at
> all. But for X86_32 the stub is missing and the build fails.
> 
> Clean that up:
> 
>   - Compile hv_apic.c only when CONFIG_X86_64=y
>   - Make the stub for hv_init_apic() available when CONFG_X86_64=n

Thanks Thomas. I was planning to send this patch today after I saw the kbuild robot mail.

Regards,

K. Y
> 
> Fixes: 6b48cb5f8347 ("X86/Hyper-V: Enlighten APIC access")
> Reported-by: kbuild test robot <lkp@xxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: Michael Kelley <mikelley@xxxxxxxxxxxxx>
> ---
>  arch/x86/hyperv/Makefile        | 3 ++-
>  arch/x86/hyperv/hv_apic.c       | 6 ------
>  arch/x86/include/asm/mshyperv.h | 7 ++++++-
>  3 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/hyperv/Makefile b/arch/x86/hyperv/Makefile
> index 00ce4df01a09..b173d404e3df 100644
> --- a/arch/x86/hyperv/Makefile
> +++ b/arch/x86/hyperv/Makefile
> @@ -1 +1,2 @@
> -obj-y		:= hv_init.o mmu.o hv_apic.o
> +obj-y			:= hv_init.o mmu.o
> +obj-$(CONFIG_X86_64)	+= hv_apic.o
> diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> index d3ff6e255924..f68855499391 100644
> --- a/arch/x86/hyperv/hv_apic.c
> +++ b/arch/x86/hyperv/hv_apic.c
> @@ -31,9 +31,6 @@
>  #include <asm/mshyperv.h>
>  #include <asm/apic.h>
> 
> -#ifdef CONFIG_X86_64
> -#if IS_ENABLED(CONFIG_HYPERV)
> -
>  static struct apic orig_apic;
> 
>  static u64 hv_apic_icr_read(void)
> @@ -257,6 +254,3 @@ void __init hv_apic_init(void)
>  		apic->icr_read  = hv_apic_icr_read;
>  	}
>  }
> -
> -#endif /* CONFIG_HYPERV */
> -#endif /* CONFIG_X86_64 */
> diff --git a/arch/x86/include/asm/mshyperv.h
> b/arch/x86/include/asm/mshyperv.h
> index 9aaa493f5756..997192131b7b 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -302,7 +302,13 @@ void hyperv_reenlightenment_intr(struct pt_regs
> *regs);
>  void set_hv_tscchange_cb(void (*cb)(void));
>  void clear_hv_tscchange_cb(void);
>  void hyperv_stop_tsc_emulation(void);
> +
> +#ifdef CONFIG_X86_64
>  void hv_apic_init(void);
> +#else
> +static inline void hv_apic_init(void) {}
> +#endif
> +
>  #else /* CONFIG_HYPERV */
>  static inline void hyperv_init(void) {}
>  static inline bool hv_is_hyperv_initialized(void) { return false; }
> @@ -311,7 +317,6 @@ static inline void hyperv_setup_mmu_ops(void) {}
>  static inline void set_hv_tscchange_cb(void (*cb)(void)) {}
>  static inline void clear_hv_tscchange_cb(void) {}
>  static inline void hyperv_stop_tsc_emulation(void) {};
> -static inline void hv_apic_init(void) {}
>  static inline struct hv_vp_assist_page *hv_get_vp_assist_page(unsigned int
> cpu)
>  {
>  	return NULL;