Re: [PATCH v8 19/24] x86/resctrl: Add helpers for system wide mon/alloc capable

["Moger, Babu" <babu.moger@amd.com>]

On 12/15/23 11:43, James Morse wrote:
> resctrl reads rdt_alloc_capable or rdt_mon_capable to determine
> whether any of the resources support the corresponding features.
> resctrl also uses the static-keys that affect the architecture's
> context-switch code to determine the same thing.
> 
> This forces another architecture to have the same static-keys.
> 
> As the static-key is enabled based on the capable flag, and none of
> the filesystem uses of these are in the scheduler path, move the
> capable flags behind helpers, and use these in the filesystem
> code instead of the static-key.
> 
> After this change, only the architecture code manages and uses
> the static-keys to ensure __resctrl_sched_in() does not need
> runtime checks.
> 
> This avoids multiple architectures having to define the same
> static-keys.
> 
> Cases where the static-key implicitly tested if the resctrl
> filesystem was mounted all have an explicit check added by a
> previous patch.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Tested-by: Peter Newman <peternewman@google.com>
> Tested-by: Babu Moger <babu.moger@amd.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>

Reviewed-by: Babu Moger <babu.moger@amd.com>

> ---
> Changes since v1:
>  * Added missing conversion in mkdir_rdt_prepare_rmid_free()
> 
> Changes since v3:
>  * Expanded the commit message.
> 
> Change since v7:
>  * Added a few missing resctrl_arch_mon_capable() that crept in during
>    a rebase.
> ---
>  arch/x86/include/asm/resctrl.h            | 13 ++++++++
>  arch/x86/kernel/cpu/resctrl/internal.h    |  2 --
>  arch/x86/kernel/cpu/resctrl/monitor.c     |  4 +--
>  arch/x86/kernel/cpu/resctrl/pseudo_lock.c |  6 ++--
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 38 +++++++++++------------
>  5 files changed, 37 insertions(+), 26 deletions(-)
> 
> diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
> index b74aa34dc9e8..12dbd2588ca7 100644
> --- a/arch/x86/include/asm/resctrl.h
> +++ b/arch/x86/include/asm/resctrl.h
> @@ -38,10 +38,18 @@ struct resctrl_pqr_state {
>  
>  DECLARE_PER_CPU(struct resctrl_pqr_state, pqr_state);
>  
> +extern bool rdt_alloc_capable;
> +extern bool rdt_mon_capable;
> +
>  DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
>  DECLARE_STATIC_KEY_FALSE(rdt_alloc_enable_key);
>  DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
>  
> +static inline bool resctrl_arch_alloc_capable(void)
> +{
> +	return rdt_alloc_capable;
> +}
> +
>  static inline void resctrl_arch_enable_alloc(void)
>  {
>  	static_branch_enable_cpuslocked(&rdt_alloc_enable_key);
> @@ -54,6 +62,11 @@ static inline void resctrl_arch_disable_alloc(void)
>  	static_branch_dec_cpuslocked(&rdt_enable_key);
>  }
>  
> +static inline bool resctrl_arch_mon_capable(void)
> +{
> +	return rdt_mon_capable;
> +}
> +
>  static inline void resctrl_arch_enable_mon(void)
>  {
>  	static_branch_enable_cpuslocked(&rdt_mon_enable_key);
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 68b9beed8e42..c4c1e1909058 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -138,8 +138,6 @@ struct rmid_read {
>  	void			*arch_mon_ctx;
>  };
>  
> -extern bool rdt_alloc_capable;
> -extern bool rdt_mon_capable;
>  extern unsigned int rdt_mon_features;
>  extern struct list_head resctrl_schema_all;
>  extern bool resctrl_mounted;
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index e3e42736fb22..95020b113ee5 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -839,7 +839,7 @@ void mbm_handle_overflow(struct work_struct *work)
>  	 * If the filesystem has been unmounted this work no longer needs to
>  	 * run.
>  	 */
> -	if (!resctrl_mounted || !static_branch_likely(&rdt_mon_enable_key))
> +	if (!resctrl_mounted || !resctrl_arch_mon_capable())
>  		goto out_unlock;
>  
>  	r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> @@ -876,7 +876,7 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms)
>  	 * When a domain comes online there is no guarantee the filesystem is
>  	 * mounted. If not, there is no need to catch counter overflow.
>  	 */
> -	if (!resctrl_mounted || !static_branch_likely(&rdt_mon_enable_key))
> +	if (!resctrl_mounted || !resctrl_arch_mon_capable())
>  		return;
>  	cpu = cpumask_any_housekeeping(&dom->cpu_mask);
>  	dom->mbm_work_cpu = cpu;
> diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> index d8f44113ed1f..8056bed033cc 100644
> --- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> +++ b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> @@ -581,7 +581,7 @@ static int rdtgroup_locksetup_user_restrict(struct rdtgroup *rdtgrp)
>  	if (ret)
>  		goto err_cpus;
>  
> -	if (rdt_mon_capable) {
> +	if (resctrl_arch_mon_capable()) {
>  		ret = rdtgroup_kn_mode_restrict(rdtgrp, "mon_groups");
>  		if (ret)
>  			goto err_cpus_list;
> @@ -628,7 +628,7 @@ static int rdtgroup_locksetup_user_restore(struct rdtgroup *rdtgrp)
>  	if (ret)
>  		goto err_cpus;
>  
> -	if (rdt_mon_capable) {
> +	if (resctrl_arch_mon_capable()) {
>  		ret = rdtgroup_kn_mode_restore(rdtgrp, "mon_groups", 0777);
>  		if (ret)
>  			goto err_cpus_list;
> @@ -776,7 +776,7 @@ int rdtgroup_locksetup_exit(struct rdtgroup *rdtgrp)
>  {
>  	int ret;
>  
> -	if (rdt_mon_capable) {
> +	if (resctrl_arch_mon_capable()) {
>  		ret = alloc_rmid(rdtgrp->closid);
>  		if (ret < 0) {
>  			rdt_last_cmd_puts("Out of RMIDs\n");
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 74a8494a0c91..89aef67588c0 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -641,13 +641,13 @@ static int __rdtgroup_move_task(struct task_struct *tsk,
>  
>  static bool is_closid_match(struct task_struct *t, struct rdtgroup *r)
>  {
> -	return (rdt_alloc_capable && (r->type == RDTCTRL_GROUP) &&
> +	return (resctrl_arch_alloc_capable() && (r->type == RDTCTRL_GROUP) &&
>  		resctrl_arch_match_closid(t, r->closid));
>  }
>  
>  static bool is_rmid_match(struct task_struct *t, struct rdtgroup *r)
>  {
> -	return (rdt_mon_capable && (r->type == RDTMON_GROUP) &&
> +	return (resctrl_arch_mon_capable() && (r->type == RDTMON_GROUP) &&
>  		resctrl_arch_match_rmid(t, r->mon.parent->closid,
>  					r->mon.rmid));
>  }
> @@ -2637,7 +2637,7 @@ static int rdt_get_tree(struct fs_context *fc)
>  
>  	closid_init();
>  
> -	if (rdt_mon_capable)
> +	if (resctrl_arch_mon_capable())
>  		flags |= RFTYPE_MON;
>  
>  	ret = rdtgroup_add_files(rdtgroup_default.kn, flags);
> @@ -2650,7 +2650,7 @@ static int rdt_get_tree(struct fs_context *fc)
>  	if (ret < 0)
>  		goto out_schemata_free;
>  
> -	if (rdt_mon_capable) {
> +	if (resctrl_arch_mon_capable()) {
>  		ret = mongroup_create_dir(rdtgroup_default.kn,
>  					  &rdtgroup_default, "mon_groups",
>  					  &kn_mongrp);
> @@ -2672,12 +2672,12 @@ static int rdt_get_tree(struct fs_context *fc)
>  	if (ret < 0)
>  		goto out_psl;
>  
> -	if (rdt_alloc_capable)
> +	if (resctrl_arch_alloc_capable())
>  		resctrl_arch_enable_alloc();
> -	if (rdt_mon_capable)
> +	if (resctrl_arch_mon_capable())
>  		resctrl_arch_enable_mon();
>  
> -	if (rdt_alloc_capable || rdt_mon_capable)
> +	if (resctrl_arch_alloc_capable() || resctrl_arch_mon_capable())
>  		resctrl_mounted = true;
>  
>  	if (is_mbm_enabled()) {
> @@ -2691,10 +2691,10 @@ static int rdt_get_tree(struct fs_context *fc)
>  out_psl:
>  	rdt_pseudo_lock_release();
>  out_mondata:
> -	if (rdt_mon_capable)
> +	if (resctrl_arch_mon_capable())
>  		kernfs_remove(kn_mondata);
>  out_mongrp:
> -	if (rdt_mon_capable)
> +	if (resctrl_arch_mon_capable())
>  		kernfs_remove(kn_mongrp);
>  out_info:
>  	kernfs_remove(kn_info);
> @@ -2949,9 +2949,9 @@ static void rdt_kill_sb(struct super_block *sb)
>  	rdtgroup_default.mode = RDT_MODE_SHAREABLE;
>  	schemata_list_destroy();
>  	rdtgroup_destroy_root();
> -	if (rdt_alloc_capable)
> +	if (resctrl_arch_alloc_capable())
>  		resctrl_arch_disable_alloc();
> -	if (rdt_mon_capable)
> +	if (resctrl_arch_mon_capable())
>  		resctrl_arch_disable_mon();
>  	resctrl_mounted = false;
>  	kernfs_kill_sb(sb);
> @@ -3331,7 +3331,7 @@ static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp)
>  {
>  	int ret;
>  
> -	if (!rdt_mon_capable)
> +	if (!resctrl_arch_mon_capable())
>  		return 0;
>  
>  	ret = alloc_rmid(rdtgrp->closid);
> @@ -3353,7 +3353,7 @@ static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp)
>  
>  static void mkdir_rdt_prepare_rmid_free(struct rdtgroup *rgrp)
>  {
> -	if (rdt_mon_capable)
> +	if (resctrl_arch_mon_capable())
>  		free_rmid(rgrp->closid, rgrp->mon.rmid);
>  }
>  
> @@ -3417,7 +3417,7 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
>  
>  	if (rtype == RDTCTRL_GROUP) {
>  		files = RFTYPE_BASE | RFTYPE_CTRL;
> -		if (rdt_mon_capable)
> +		if (resctrl_arch_mon_capable())
>  			files |= RFTYPE_MON;
>  	} else {
>  		files = RFTYPE_BASE | RFTYPE_MON;
> @@ -3526,7 +3526,7 @@ static int rdtgroup_mkdir_ctrl_mon(struct kernfs_node *parent_kn,
>  
>  	list_add(&rdtgrp->rdtgroup_list, &rdt_all_groups);
>  
> -	if (rdt_mon_capable) {
> +	if (resctrl_arch_mon_capable()) {
>  		/*
>  		 * Create an empty mon_groups directory to hold the subset
>  		 * of tasks and cpus to monitor.
> @@ -3581,14 +3581,14 @@ static int rdtgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
>  	 * allocation is supported, add a control and monitoring
>  	 * subdirectory
>  	 */
> -	if (rdt_alloc_capable && parent_kn == rdtgroup_default.kn)
> +	if (resctrl_arch_alloc_capable() && parent_kn == rdtgroup_default.kn)
>  		return rdtgroup_mkdir_ctrl_mon(parent_kn, name, mode);
>  
>  	/*
>  	 * If RDT monitoring is supported and the parent directory is a valid
>  	 * "mon_groups" directory, add a monitoring subdirectory.
>  	 */
> -	if (rdt_mon_capable && is_mon_groups(parent_kn, name))
> +	if (resctrl_arch_mon_capable() && is_mon_groups(parent_kn, name))
>  		return rdtgroup_mkdir_mon(parent_kn, name, mode);
>  
>  	return -EPERM;
> @@ -3923,7 +3923,7 @@ void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d)
>  	 * If resctrl is mounted, remove all the
>  	 * per domain monitor data directories.
>  	 */
> -	if (resctrl_mounted && static_branch_unlikely(&rdt_mon_enable_key))
> +	if (resctrl_mounted && resctrl_arch_mon_capable())
>  		rmdir_mondata_subdir_allrdtgrp(r, d->id);
>  
>  	if (is_mbm_enabled())
> @@ -4006,7 +4006,7 @@ int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d)
>  	 * by rdt_get_tree() calling mkdir_mondata_all().
>  	 * If resctrl is mounted, add per domain monitor data directories.
>  	 */
> -	if (resctrl_mounted && static_branch_unlikely(&rdt_mon_enable_key))
> +	if (resctrl_mounted && resctrl_arch_mon_capable())
>  		mkdir_mondata_subdir_allrdtgrp(r, d);
>  
>  	return 0;

-- 
Thanks
Babu Moger