RE: [PATCH v2 1/2] asm-generic/hyperv: provide cpumask_to_vpset_noself

From: Michael Kelley <mikelley@microsoft.com>
To: Wei Liu <wei.liu@kernel.org>,
	Linux on Hyper-V List <linux-hyperv@vger.kernel.org>
Cc: KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Dexuan Cui <decui@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Arnd Bergmann <arnd@arndb.de>,
	"open list:GENERIC INCLUDE/ASM HEADER FILES" 
	<linux-arch@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2 1/2] asm-generic/hyperv: provide cpumask_to_vpset_noself
Date: Sat, 11 Sep 2021 15:06:18 +0000	[thread overview]
Message-ID: <MWHPR21MB15933CFA486898817B7E396AD7D79@MWHPR21MB1593.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20210910185714.299411-2-wei.liu@kernel.org>

From: Wei Liu <wei.liu@kernel.org> Sent: Friday, September 10, 2021 11:57 AM
> 
> This is a new variant which removes `self' cpu from the vpset. It will
> be used in Hyper-V enlightened IPI code.
> 
> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> ---
> Provide a new variant instead of adding a new parameter because it makes
> it easier to backport -- we don't need to fix the users of
> cpumask_to_vpset.
> 
> v2:
> 1. Rename function
> 2. Add preemptible check
> ---
>  include/asm-generic/mshyperv.h | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index 9a000ba2bb75..9a134806f1d5 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -184,10 +184,12 @@ static inline int hv_cpu_number_to_vp_number(int cpu_number)
>  	return hv_vp_index[cpu_number];
>  }
> 
> -static inline int cpumask_to_vpset(struct hv_vpset *vpset,
> -				    const struct cpumask *cpus)
> +static inline int __cpumask_to_vpset(struct hv_vpset *vpset,
> +				    const struct cpumask *cpus,
> +				    bool exclude_self)
>  {
>  	int cpu, vcpu, vcpu_bank, vcpu_offset, nr_bank = 1;
> +	int this_cpu = smp_processor_id();
> 
>  	/* valid_bank_mask can represent up to 64 banks */
>  	if (hv_max_vp_index / 64 >= 64)
> @@ -205,6 +207,8 @@ static inline int cpumask_to_vpset(struct hv_vpset *vpset,
>  	 * Some banks may end up being empty but this is acceptable.
>  	 */
>  	for_each_cpu(cpu, cpus) {
> +		if (exclude_self && cpu == this_cpu)
> +			continue;
>  		vcpu = hv_cpu_number_to_vp_number(cpu);
>  		if (vcpu == VP_INVAL)
>  			return -1;
> @@ -219,6 +223,19 @@ static inline int cpumask_to_vpset(struct hv_vpset *vpset,
>  	return nr_bank;
>  }
> 
> +static inline int cpumask_to_vpset(struct hv_vpset *vpset,
> +				    const struct cpumask *cpus)
> +{
> +	return __cpumask_to_vpset(vpset, cpus, false);
> +}
> +
> +static inline int cpumask_to_vpset_noself(struct hv_vpset *vpset,
> +				    const struct cpumask *cpus)
> +{
> +	WARN_ON_ONCE(preemptible());
> +	return __cpumask_to_vpset(vpset, cpus, true);
> +}
> +
>  void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die);
>  bool hv_is_hyperv_initialized(void);
>  bool hv_is_hibernation_supported(void);
> --
> 2.30.2

Reviewed-by: Michael Kelley <mikelley@microsoft.com>