Re: [PATCH 3/4] Drivers: hv: vmbus: Add hooks for per-CPU IRQ

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Nov 22, 2018 at 03:10:58AM +0000, kys@linuxonhyperv.com wrote:
> From: Michael Kelley <mikelley@microsoft.com>
> 
> Add hooks to enable/disable a per-CPU IRQ for VMbus. These hooks
> are in the architecture independent setup and shutdown paths for
> Hyper-V, and are needed by Linux guests on Hyper-V on ARM64.  The
> x86/x64 implementation is null because VMbus interrupts on x86/x64
> don't use an IRQ.
> 
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
>  arch/x86/include/asm/mshyperv.h | 4 ++++
>  drivers/hv/hv.c                 | 2 ++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 0d6271cce198..8d97bd3a13a6 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -109,6 +109,10 @@ void hyperv_vector_handler(struct pt_regs *regs);
>  void hv_setup_vmbus_irq(void (*handler)(void));
>  void hv_remove_vmbus_irq(void);
>  
> +/* On x86/x64, there isn't a real IRQ to be enabled/disable */
> +static inline void hv_enable_vmbus_irq(void) {}
> +static inline void hv_disable_vmbus_irq(void) {}
> +
>  void hv_setup_kexec_handler(void (*handler)(void));
>  void hv_remove_kexec_handler(void);
>  void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs));
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 166c2501de17..d0bb09a4bd73 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -307,6 +307,7 @@ int hv_synic_init(unsigned int cpu)
>  	hv_set_siefp(siefp.as_uint64);
>  
>  	/* Setup the shared SINT. */
> +	hv_enable_vmbus_irq();
>  	hv_get_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
>  
>  	shared_sint.vector = HYPERVISOR_CALLBACK_VECTOR;
> @@ -434,6 +435,7 @@ int hv_synic_cleanup(unsigned int cpu)
>  	/* Disable the global synic bit */
>  	sctrl.enable = 0;
>  	hv_set_synic_state(sctrl.as_uint64);
> +	hv_disable_vmbus_irq();
>  
>  	return 0;
>  }
> -- 
> 2.19.1

You created "null" hooks that do nothing, for no one in this patch
series, why?

Add them when they are needed not now.  If I saw this code in the tree,
I would just go delete it as it is because it is not used at all.

thanks,

greg k-h