Date: Mon, 15 Apr 2024 15:28:18 -0500
From: "Moger, Babu" <babu.moger@....com>
To: James Morse <james.morse@....com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Cc: Fenghua Yu <fenghua.yu@...el.com>,
 Reinette Chatre <reinette.chatre@...el.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, H Peter Anvin <hpa@...or.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>
Subject: Re: [PATCH v1 02/31] x86/resctrl: Add a helper to avoid reaching into
 the arch code resource list

Hi James/Dave,

On 3/21/24 11:50, James Morse wrote:
> Resctrl occasionally wants to know something about a specific resource,
> in these cases it reaches into the arch code's rdt_resources_all[]
> array.
> 
> Once the filesystem parts of resctrl are moved to /fs/, this means it
> will need visibility of the architecture specific struct
> resctrl_hw_resource definition, and the array of all resources.
> All architectures would also need a r_resctrl member in this struct.
> 
> Instead, abstract this via a helper to allow architectures to do
> different things here. Move the level enum to the resctrl header and
> add a helper to retrieve the struct rdt_resource by 'rid'.
> 
> resctrl_arch_get_resource() should not return NULL for any value in
> the enum, it may instead return a dummy resource that is
> !alloc_enabled && !mon_enabled.

Nit.
You may want to drop the second half of the statement. We don't have a
dummy resource.

> 
> Signed-off-by: James Morse <james.morse@....com>
> ---
>  arch/x86/kernel/cpu/resctrl/core.c        | 10 +++++++++-
>  arch/x86/kernel/cpu/resctrl/ctrlmondata.c |  2 +-
>  arch/x86/kernel/cpu/resctrl/internal.h    | 10 ----------
>  arch/x86/kernel/cpu/resctrl/monitor.c     |  8 ++++----
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 15 +++++++--------
>  include/linux/resctrl.h                   | 17 +++++++++++++++++
>  6 files changed, 38 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 83e40341583e..b773b3bdebe3 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -122,6 +122,14 @@ struct rdt_hw_resource rdt_resources_all[] = {
>  	},
>  };
>  
> +struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l)
> +{
> +	if (l >= RDT_NUM_RESOURCES)
> +		return NULL;
> +
> +	return &rdt_resources_all[l].r_resctrl;
> +}
> +
>  /*
>   * cache_alloc_hsw_probe() - Have to probe for Intel haswell server CPUs
>   * as they do not have CPUID enumeration support for Cache allocation.
> @@ -169,7 +177,7 @@ static inline void cache_alloc_hsw_probe(void)
>  bool is_mba_sc(struct rdt_resource *r)
>  {
>  	if (!r)
> -		return rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl.membw.mba_sc;
> +		r = resctrl_arch_get_resource(RDT_RESOURCE_MBA);
>  
>  	/*
>  	 * The software controller support is only applicable to MBA resource.
> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> index 7997b47743a2..788ac0395645 100644
> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> @@ -599,7 +599,7 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
>  	domid = md.u.domid;
>  	evtid = md.u.evtid;
>  
> -	r = &rdt_resources_all[resid].r_resctrl;
> +	r = resctrl_arch_get_resource(resid);
>  	d = rdt_find_domain(r, domid, NULL);
>  	if (IS_ERR_OR_NULL(d)) {
>  		ret = -ENOENT;
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index c99f26ebe7a6..65990def6c79 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -466,16 +466,6 @@ extern struct rdt_hw_resource rdt_resources_all[];
>  extern struct rdtgroup rdtgroup_default;
>  extern struct dentry *debugfs_resctrl;
>  
> -enum resctrl_res_level {
> -	RDT_RESOURCE_L3,
> -	RDT_RESOURCE_L2,
> -	RDT_RESOURCE_MBA,
> -	RDT_RESOURCE_SMBA,
> -
> -	/* Must be the last */
> -	RDT_NUM_RESOURCES,
> -};
> -
>  static inline struct rdt_resource *resctrl_inc(struct rdt_resource *res)
>  {
>  	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(res);
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index c34a35ec0f03..06565153ceb2 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -321,7 +321,7 @@ static void limbo_release_entry(struct rmid_entry *entry)
>   */
>  void __check_limbo(struct rdt_domain *d, bool force_free)
>  {
> -	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> +	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
>  	u32 idx_limit = resctrl_arch_system_num_rmid_idx();
>  	struct rmid_entry *entry;
>  	u32 idx, cur_idx = 1;
> @@ -467,7 +467,7 @@ int alloc_rmid(u32 closid)
>  
>  static void add_rmid_to_limbo(struct rmid_entry *entry)
>  {
> -	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> +	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
>  	struct rdt_domain *d;
>  	u32 idx;
>  
> @@ -669,7 +669,7 @@ static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
>  	if (!is_mbm_local_enabled())
>  		return;
>  
> -	r_mba = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
> +	r_mba = resctrl_arch_get_resource(RDT_RESOURCE_MBA);
>  
>  	closid = rgrp->closid;
>  	rmid = rgrp->mon.rmid;
> @@ -839,7 +839,7 @@ void mbm_handle_overflow(struct work_struct *work)
>  	if (!resctrl_mounted || !resctrl_arch_mon_capable())
>  		goto out_unlock;
>  
> -	r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> +	r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
>  	d = container_of(work, struct rdt_domain, mbm_over.work);
>  
>  	list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 1767c1affa60..45372b6a6215 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -2253,7 +2253,7 @@ static void l2_qos_cfg_update(void *arg)
>  
>  static inline bool is_mba_linear(void)
>  {
> -	return rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl.membw.delay_linear;
> +	return resctrl_arch_get_resource(RDT_RESOURCE_MBA)->membw.delay_linear;
>  }
>  
>  static int set_cache_qos_cfg(int level, bool enable)
> @@ -2341,7 +2341,7 @@ static void mba_sc_domain_destroy(struct rdt_resource *r,
>   */
>  static bool supports_mba_mbps(void)
>  {
> -	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
> +	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_MBA);
>  
>  	return (is_mbm_local_enabled() &&
>  		r->alloc_capable && is_mba_linear());
> @@ -2353,7 +2353,7 @@ static bool supports_mba_mbps(void)
>   */
>  static int set_mba_sc(bool mba_sc)
>  {
> -	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
> +	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_MBA);
>  	u32 num_closid = resctrl_arch_get_num_closid(r);
>  	struct rdt_domain *d;
>  	int i;
> @@ -2625,10 +2625,10 @@ static void schemata_list_destroy(void)
>  
>  static int rdt_get_tree(struct fs_context *fc)
>  {
> +	struct rdt_resource *l3 = resctrl_arch_get_resource(RDT_RESOURCE_L3);

Its is probably best to keep the resource name as r here to be consistent
with other changes.

>  	struct rdt_fs_context *ctx = rdt_fc2context(fc);
>  	unsigned long flags = RFTYPE_CTRL_BASE;
>  	struct rdt_domain *dom;
> -	struct rdt_resource *r;
>  	int ret;
>  
>  	cpus_read_lock();
> @@ -2701,8 +2701,7 @@ static int rdt_get_tree(struct fs_context *fc)
>  		resctrl_mounted = true;
>  
>  	if (is_mbm_enabled()) {
> -		r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> -		list_for_each_entry(dom, &r->domains, list)
> +		list_for_each_entry(dom, &l3->domains, list)
>  			mbm_setup_overflow_handler(dom, MBM_OVERFLOW_INTERVAL,
>  						   RESCTRL_PICK_ANY_CPU);
>  	}
> @@ -3878,7 +3877,7 @@ static int rdtgroup_show_options(struct seq_file *seq, struct kernfs_root *kf)
>  	if (resctrl_arch_get_cdp_enabled(RDT_RESOURCE_L2))
>  		seq_puts(seq, ",cdpl2");
>  
> -	if (is_mba_sc(&rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl))
> +	if (is_mba_sc(resctrl_arch_get_resource(RDT_RESOURCE_MBA)))
>  		seq_puts(seq, ",mba_MBps");
>  
>  	if (resctrl_debug)
> @@ -4068,7 +4067,7 @@ static void clear_childcpus(struct rdtgroup *r, unsigned int cpu)
>  
>  void resctrl_offline_cpu(unsigned int cpu)
>  {
> -	struct rdt_resource *l3 = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> +	struct rdt_resource *l3 = resctrl_arch_get_resource(RDT_RESOURCE_L3);
>  	struct rdtgroup *rdtgrp;
>  	struct rdt_domain *d;
>  
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index a365f67131ec..168cc9510069 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -36,6 +36,16 @@ enum resctrl_conf_type {
>  	CDP_DATA,
>  };
>  
> +enum resctrl_res_level {
> +	RDT_RESOURCE_L3,
> +	RDT_RESOURCE_L2,
> +	RDT_RESOURCE_MBA,
> +	RDT_RESOURCE_SMBA,
> +
> +	/* Must be the last */
> +	RDT_NUM_RESOURCES,
> +};
> +
>  #define CDP_NUM_TYPES	(CDP_DATA + 1)
>  
>  /*
> @@ -190,6 +200,13 @@ struct rdt_resource {
>  	bool			cdp_capable;
>  };
>  
> +/*
> + * Get the resource that exists at this level. If the level is not supported
> + * a dummy/not-capable resource can be returned. Levels >= RDT_NUM_RESOURCES
> + * will return NULL.
> + */
> +struct rdt_resource *resctrl_arch_get_resource(enum resctrl_res_level l);
> +
>  /**
>   * struct resctrl_schema - configuration abilities of a resource presented to
>   *			   user-space

-- 
Thanks
Babu Moger

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