Subject: Re: [PATCH] powerpc/sched: Cleanup vcpu_is_preempted()

From: Srikar Dronamraju <[email-masked]>
Date: Tue, 14 Nov 2023 15:16:22 +0530

* Aneesh Kumar K.V <[email-masked]> [2023-11-14 12:42:19]:

> No functional change in this patch. A helper is added to find if
> vcpu is dispatched by hypervisor. Use that instead of opencoding.
> Also clarify some of the comments.
> 
> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
> ---
>  arch/powerpc/include/asm/paravirt.h | 33 ++++++++++++++++++++++-------
>  1 file changed, 25 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h
> index ac4279208d63..b78b82d66057 100644
> --- a/arch/powerpc/include/asm/paravirt.h
> +++ b/arch/powerpc/include/asm/paravirt.h
> @@ -76,6 +76,17 @@ static inline bool is_vcpu_idle(int vcpu)
>  {
>  	return lppaca_of(vcpu).idle;
>  }
> +
> +static inline bool vcpu_is_dispatched(int vcpu)
> +{
> +	/*
> +	 * This is the yield_count.  An "odd" value (low bit on) means that
> +	 * the processor is yielded (either because of an OS yield or a
> +	 * hypervisor preempt).  An even value implies that the processor is
> +	 * currently executing.
> +	 */
> +	return (!(yield_count_of(vcpu) & 1));
> +}
>  #else
>  static inline bool is_shared_processor(void)
>  {
> @@ -109,6 +120,10 @@ static inline bool is_vcpu_idle(int vcpu)
>  {
>  	return false;
>  }
> +static inline bool vcpu_is_dispatched(int vcpu)
> +{
> +	return true;
> +}
>  #endif

If we are introducing vcpu_is_dispatched, we should remove 
yield_count_of() and use vcpu_is_dispatched everwhere

No point in having yield_count_of() and vcpu_is_dispatched, since
yield_count_of() is only used to check if we are running in OS or not.

-- 
Thanks and Regards
Srikar Dronamraju