linux-kernel - Re: [PATCH v4 20/24] x86/resctrl: Add cpu online callback for resctrl work

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Date:   Thu, 15 Jun 2023 15:23:31 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     James Morse <james.morse@....com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        <shameerali.kolothum.thodi@...wei.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        <carl@...amperecomputing.com>, <lcherian@...vell.com>,
        <bobo.shaobowang@...wei.com>, <tan.shaopeng@...itsu.com>,
        <xingxin.hx@...nanolis.org>, <baolin.wang@...ux.alibaba.com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>, <peternewman@...gle.com>,
        <dfustini@...libre.com>
Subject: Re: [PATCH v4 20/24] x86/resctrl: Add cpu online callback for resctrl
 work

Hi James,

On 5/25/2023 11:02 AM, James Morse wrote:
> The resctrl architecture specific code may need to create a domain when
> a CPU comes online, it also needs to reset the CPUs PQR_ASSOC register.
> The resctrl filesystem code needs to update the rdtgroup_default cpu
> mask when cpus are brought online.

CPU mask when CPUs

> 
> Currently this is all done in one function, resctrl_online_cpu().
> This will need to be split into architecture and filesystem parts
> before resctrl can be moved to /fs/.
> 
> Pull the rdtgroup_default update work out as a filesystem specific
> cpu_online helper. resctrl_online_cpu() is the obvious name for this,
> which means the version in core.c needs renaming.
> 
> resctrl_online_cpu() is called by the arch code once it has done the
> work to add the new cpu to any domains.

CPU

> 
> In future patches, resctrl_online_cpu() will take the rdtgroup_mutex
> itself.
> 
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Signed-off-by: James Morse <james.morse@....com>
> ---
> Changes since v3:
>  * Renamed err to ret
> ---
>  arch/x86/kernel/cpu/resctrl/core.c     | 11 ++++++-----
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 10 ++++++++++
>  include/linux/resctrl.h                |  1 +
>  3 files changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 4bea032d072e..e00f3542e60e 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -603,19 +603,20 @@ static void clear_closid_rmid(int cpu)
>  	wrmsr(MSR_IA32_PQR_ASSOC, 0, RESCTRL_RESERVED_CLOSID);
>  }
>  
> -static int resctrl_online_cpu(unsigned int cpu)
> +static int resctrl_arch_online_cpu(unsigned int cpu)
>  {
>  	struct rdt_resource *r;
> +	int ret;
>  
>  	mutex_lock(&rdtgroup_mutex);
>  	for_each_capable_rdt_resource(r)
>  		domain_add_cpu(cpu, r);
> -	/* The cpu is set in default rdtgroup after online. */
> -	cpumask_set_cpu(cpu, &rdtgroup_default.cpu_mask);
>  	clear_closid_rmid(cpu);
> +
> +	ret = resctrl_online_cpu(cpu);
>  	mutex_unlock(&rdtgroup_mutex);
>  
> -	return 0;
> +	return ret;
>  }
>  
>  static void clear_childcpus(struct rdtgroup *r, unsigned int cpu)
> @@ -965,7 +966,7 @@ static int __init resctrl_late_init(void)
>  
>  	state = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
>  				  "x86/resctrl/cat:online:",
> -				  resctrl_online_cpu, resctrl_offline_cpu);
> +				  resctrl_arch_online_cpu, resctrl_offline_cpu);
>  	if (state < 0)
>  		return state;
>  
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 5330c0bdeffc..7c3de5ea0482 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -3725,6 +3725,16 @@ int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d)
>  	return 0;
>  }
>  
> +int resctrl_online_cpu(unsigned int cpu)
> +{
> +	lockdep_assert_held(&rdtgroup_mutex);
> +
> +	/* The cpu is set in default rdtgroup after online. */

I know that you just copied this but please use CPU instead of cpu.

Reinette