linux-kernel - Re: [PATCH v5 14/40] x86/resctrl: Add a resctrl helper to reset all the resources

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Message-ID: <a0ed3b9b-c035-440b-8244-7e6a5c4009c9@intel.com>
Date: Wed, 23 Oct 2024 14:32:31 -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>, <baolin.wang@...ux.alibaba.com>, Jamie Iles
	<quic_jiles@...cinc.com>, Xin Hao <xhao@...ux.alibaba.com>,
	<peternewman@...gle.com>, <dfustini@...libre.com>, <amitsinght@...vell.com>,
	David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
	"Dave Martin" <dave.martin@....com>, Shaopeng Tan
	<tan.shaopeng@...fujitsu.com>
Subject: Re: [PATCH v5 14/40] x86/resctrl: Add a resctrl helper to reset all
 the resources

Hi James,

On 10/4/24 11:03 AM, James Morse wrote:
> On umount(), resctrl resets each resource back to its default
> configuration. It only ever does this for all resources in one go.
> 
> reset_all_ctrls() is architecture specific as it works with struct
> rdt_hw_resource.
> 
> Add an architecture helper to reset all resources.
> 
> Co-developed-by: Dave Martin <Dave.Martin@....com>
> Signed-off-by: Dave Martin <Dave.Martin@....com>
> Signed-off-by: James Morse <james.morse@....com>
> Tested-by: Carl Worth <carl@...amperecomputing.com> # arm64
> Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> ---
> Changes since v1:
>  * Rename the for_each_capable_rdt_resource() introduced in the new
>    function resctrl_arch_reset_resources(), back to
>    for_each_alloc_capable_rdt_resource() as it was in the original code.
> 
>    The change looked unintentional; and presumably a resource that does
>    not support resource allocation doesn't have any properties to
>    reset...
> ---
>  arch/x86/include/asm/resctrl.h         |  2 ++
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 16 +++++++++++-----
>  2 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
> index 52f2326e2b1e..5622943f6354 100644
> --- a/arch/x86/include/asm/resctrl.h
> +++ b/arch/x86/include/asm/resctrl.h
> @@ -16,6 +16,8 @@
>   */
>  #define X86_RESCTRL_EMPTY_CLOSID         ((u32)~0)
>  
> +void resctrl_arch_reset_resources(void);
> +
>  /**
>   * struct resctrl_pqr_state - State cache for the PQR MSR
>   * @cur_rmid:		The cached Resource Monitoring ID
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 61c8add103fe..a15198f90b29 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -2883,6 +2883,14 @@ static int reset_all_ctrls(struct rdt_resource *r)
>  	return 0;
>  }
>  
> +void resctrl_arch_reset_resources(void)
> +{
> +	struct rdt_resource *r;
> +
> +	for_each_alloc_capable_rdt_resource(r)
> +		reset_all_ctrls(r);
> +}

Wouldn't this require all archs to have a duplicate helper as above with
only the resctrl_all_ctrls() actually being arch specific? 
What if it is instead:
	resctrl_reset_alloc_resources() or reset_alloc_resources() or ...
	{
		struct rdt_resource *r;
	
		for_each_alloc_capable_rdt_resource(r)
			resctrl_arch_reset_all_ctrls(r);
	}

With above archs only need to implement the actual reset code.


> +
>  /*
>   * Move tasks from one to the other group. If @from is NULL, then all tasks
>   * in the systems are moved unconditionally (used for teardown).
> @@ -2992,16 +3000,14 @@ static void rmdir_all_sub(void)
>  
>  static void rdt_kill_sb(struct super_block *sb)
>  {
> -	struct rdt_resource *r;
> -
>  	cpus_read_lock();
>  	mutex_lock(&rdtgroup_mutex);
>  
>  	rdt_disable_ctx();
>  
> -	/*Put everything back to default values. */
> -	for_each_alloc_capable_rdt_resource(r)
> -		reset_all_ctrls(r);
> +	/* Put everything back to default values. */
> +	resctrl_arch_reset_resources();
> +
>  	rmdir_all_sub();
>  	rdt_pseudo_lock_release();
>  	rdtgroup_default.mode = RDT_MODE_SHAREABLE;

Reinette