linux-kernel - Re: [PATCH] x86/resctrl: Check monitoring static key in MBM overflow handler

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Date:   Thu, 12 Dec 2019 03:18:37 +0800
From:   Xiaochen Shen <xiaochen.shen@...el.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        tony.luck@...el.com, fenghua.yu@...el.com,
        reinette.chatre@...el.com
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, pei.p.jia@...el.com,
        Xiaochen Shen <xiaochen.shen@...el.com>
Subject: Re: [PATCH] x86/resctrl: Check monitoring static key in MBM overflow
 handler

Hi,

I am sorry I sent out a wrong version of patch.
Please ignore this patch. I will resend soon.


On 12/12/2019 1:41, Xiaochen Shen wrote:
> Currently, there are three static keys in resctrl file system:
> rdt_mon_enable_key and rdt_alloc_enable_key indicate if monitoring
> feature and allocation feature is enabled respectively. rdt_enable_key
> is enabled when either monitoring feature or allocation feature is
> enabled.
> 
> If no monitoring feature is supported (either hardware doesn't support
> monitoring feature or the feature is disabled by kernel command line
> option "rdt="), rdt_enable_key is still enabled but rdt_mon_enable_key
> is disabled.
> 
> MBM is a monitoring feature. MBM overflow handler intends to check if
> monitoring feature is not enabled for fast return. So the accurate check
> here is to check rdt_mon_enable_key instead of rdt_enable_key.
> 
> Fixes: e33026831bdb ("x86/intel_rdt/mbm: Handle counter overflow")
> Signed-off-by: Xiaochen Shen <xiaochen.shen@...el.com>
> Reviewed-by: Fenghua Yu <fenghua.yu@...el.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> ---
>   arch/x86/kernel/cpu/resctrl/internal.h | 1 +
>   arch/x86/kernel/cpu/resctrl/monitor.c  | 4 ++--
>   2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index e49b77283924..181c992f448c 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -57,6 +57,7 @@ static inline struct rdt_fs_context *rdt_fc2context(struct fs_context *fc)
>   }
>   
>   DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
> +DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
>   
>   /**
>    * struct mon_evt - Entry in the event list of a resource
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 397206f23d14..773124b0e18a 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -514,7 +514,7 @@ void mbm_handle_overflow(struct work_struct *work)
>   
>   	mutex_lock(&rdtgroup_mutex);
>   
> -	if (!static_branch_likely(&rdt_enable_key))
> +	if (!static_branch_likely(&rdt_mon_enable_key))
>   		goto out_unlock;
>   
>   	d = get_domain_from_cpu(cpu, &rdt_resources_all[RDT_RESOURCE_L3]);
> @@ -543,7 +543,7 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms)
>   	unsigned long delay = msecs_to_jiffies(delay_ms);
>   	int cpu;
>   
> -	if (!static_branch_likely(&rdt_enable_key))
> +	if (!static_branch_likely(&rdt_mon_enable_key))
>   		return;
>   	cpu = cpumask_any(&dom->cpu_mask);
>   	dom->mbm_work_cpu = cpu;
> 

-- 
Best regards,
Xiaochen