[PATCH v2 08/15] Drivers: hv: Move hv_call_(get|set)_vp_registers() declarations

[Michael Kelley]

From: Naman Jain <namjain at linux.microsoft.com> Sent: Thursday, April 23, 2026 5:42 AM
> 
> Move hv_call_get_vp_registers() and hv_call_set_vp_registers()
> declarations from drivers/hv/mshv.h to include/asm-generic/mshyperv.h.
> 
> These functions are defined in mshv_common.c and are going to be called
> from both drivers/hv/ and arch/x86/hyperv/hv_vtl.c. The latter never
> included mshv.h, relying on implicit declaration visibility. Moving the
> declarations to the arch-generic Hyper-V header makes them properly
> visible to all architecture-specific callers.
> 
> Provide static inline stubs returning -EOPNOTSUPP when neither
> CONFIG_MSHV_ROOT nor CONFIG_MSHV_VTL is enabled.

Looking at the drivers/hv/Kconfig, it's possible to build with
CONFIG_HYPERV_VTL_MODE=y, but not CONFIG_MSHV_VTL. In such a
case, mshv_common.o doesn't get built, which is why the stubs are
needed. Is such a configuration desirable for some scenarios?

I wonder if having CONFIG_HYPERV_VTL_MODE force the building of
mshv_common.o would be a better approach. Then the stubs wouldn't
be needed. The "ifneq" statement in drivers/hv/Makefile could use
CONFIG_HYPERV_VTL_MODE instead of CONFIG_MSHV_VTL, and
everything would be good since CONFIG_MSHV_VTL depends on
CONFIG_HYPERV_VTL_MODE.

> 
> Signed-off-by: Naman Jain <namjain at linux.microsoft.com>
> ---
>  drivers/hv/mshv.h              |  8 --------
>  include/asm-generic/mshyperv.h | 26 ++++++++++++++++++++++++++
>  2 files changed, 26 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/hv/mshv.h b/drivers/hv/mshv.h
> index d4813df92b9c..0fcb7f9ba6a9 100644
> --- a/drivers/hv/mshv.h
> +++ b/drivers/hv/mshv.h
> @@ -14,14 +14,6 @@
>  	memchr_inv(&((STRUCT).MEMBER), \
>  		   0, sizeof_field(typeof(STRUCT), MEMBER))
> 
> -int hv_call_get_vp_registers(u32 vp_index, u64 partition_id, u16 count,
> -			     union hv_input_vtl input_vtl,
> -			     struct hv_register_assoc *registers);
> -
> -int hv_call_set_vp_registers(u32 vp_index, u64 partition_id, u16 count,
> -			     union hv_input_vtl input_vtl,
> -			     struct hv_register_assoc *registers);
> -
>  int hv_call_get_partition_property(u64 partition_id, u64 property_code,
>  				   u64 *property_value);
> 
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index 8cdf2a9fbdfb..ef0b9466808c 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -394,6 +394,32 @@ static inline int hv_deposit_memory(u64 partition_id, u64
> status)
>  	return hv_deposit_memory_node(NUMA_NO_NODE, partition_id, status);
>  }
> 
> +#if IS_ENABLED(CONFIG_MSHV_ROOT) || IS_ENABLED(CONFIG_MSHV_VTL)
> +int hv_call_get_vp_registers(u32 vp_index, u64 partition_id, u16 count,
> +			     union hv_input_vtl input_vtl,
> +			     struct hv_register_assoc *registers);
> +
> +int hv_call_set_vp_registers(u32 vp_index, u64 partition_id, u16 count,
> +			     union hv_input_vtl input_vtl,
> +			     struct hv_register_assoc *registers);
> +#else
> +static inline int hv_call_get_vp_registers(u32 vp_index, u64 partition_id,
> +					   u16 count,
> +					   union hv_input_vtl input_vtl,
> +					   struct hv_register_assoc *registers)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static inline int hv_call_set_vp_registers(u32 vp_index, u64 partition_id,
> +					   u16 count,
> +					   union hv_input_vtl input_vtl,
> +					   struct hv_register_assoc *registers)
> +{
> +	return -EOPNOTSUPP;
> +}
> +#endif /* CONFIG_MSHV_ROOT || CONFIG_MSHV_VTL */
> +
>  #if IS_ENABLED(CONFIG_HYPERV_VTL_MODE)
>  u8 __init get_vtl(void);
>  void mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0);
> --
> 2.43.0
>