Re: [PATCH v3 6/7] x86/resctrl: Introduce interface to display io_alloc CBMs

[Reinette Chatre]

Hi Babu,

On 1/30/25 1:20 PM, Babu Moger wrote:
> The io_alloc feature in resctrl enables system software to configure
> the portion of the L3 cache allocated for I/O traffic.
> 
> Add the interface to display CBMs (Capacity Bit Mask) of io_alloc
> feature.
> 
> When CDP is enabled, io_alloc routes traffic using the highest CLOSID
> which corresponds to CDP_CODE. Add a check for the CDP resource type.

It is not obvious to me what is meant with "highest CLOSID
which corresponds to CDP_CODE" ... how about "highest CLOSID used by
a L3CODE resource"?

> 
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---
> v3: Minor changes due to changes in resctrl_arch_get_io_alloc_enabled()
>     and resctrl_io_alloc_closid_get().
>     Added the check to verify CDP resource type.
>     Updated the commit log.
> 
> v2: Fixed to display only on L3 resources.
>     Added the locks while processing.
>     Rename the displat to io_alloc_cbm (from sdciae_cmd).
> ---
>  arch/x86/kernel/cpu/resctrl/core.c        |  2 ++
>  arch/x86/kernel/cpu/resctrl/ctrlmondata.c |  2 +-
>  arch/x86/kernel/cpu/resctrl/internal.h    |  1 +
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 38 +++++++++++++++++++++++
>  4 files changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 88bc95c14ea8..030f738dea8d 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -311,6 +311,8 @@ static void rdt_set_io_alloc_capable(struct rdt_resource *r)
>  	r->cache.io_alloc_capable = true;
>  	resctrl_file_fflags_init("io_alloc",
>  				 RFTYPE_CTRL_INFO | RFTYPE_RES_CACHE);
> +	resctrl_file_fflags_init("io_alloc_cbm",
> +				 RFTYPE_CTRL_INFO | RFTYPE_RES_CACHE);
>  }
>  
>  static void rdt_get_cdp_l3_config(void)
> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> index 536351159cc2..d272dea43924 100644
> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
> @@ -444,7 +444,7 @@ u32 resctrl_arch_get_config(struct rdt_resource *r, struct rdt_ctrl_domain *d,
>  	return hw_dom->ctrl_val[idx];
>  }
>  
> -static void show_doms(struct seq_file *s, struct resctrl_schema *schema, int closid)
> +void show_doms(struct seq_file *s, struct resctrl_schema *schema, int closid)
>  {
>  	struct rdt_resource *r = schema->res;
>  	struct rdt_ctrl_domain *dom;
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 61bc609e932b..07cf8409174d 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -668,4 +668,5 @@ void resctrl_file_fflags_init(const char *config, unsigned long fflags);
>  void rdt_staged_configs_clear(void);
>  bool closid_allocated(unsigned int closid);
>  int resctrl_find_cleanest_closid(void);
> +void show_doms(struct seq_file *s, struct resctrl_schema *schema, int closid);
>  #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 37295dd14abe..81b9d8c5dabf 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1967,6 +1967,38 @@ static ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf,
>  	return ret ?: nbytes;
>  }
>  
> +static int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of,
> +				     struct seq_file *seq, void *v)
> +{
> +	struct resctrl_schema *s = of->kn->parent->priv;
> +	struct rdt_resource *r = s->res;
> +	u32 io_alloc_closid;
> +	int ret = 0;
> +
> +	if (!r->cache.io_alloc_capable || s->conf_type == CDP_DATA) {
> +		rdt_last_cmd_puts("io_alloc feature is not supported on the resource\n");

rdt_last_cmd_puts() has to be called with rdtgroup_mutex held, also clear it before use.

> +		return -EINVAL;

How about ENODEV?

> +	}
> +
> +	cpus_read_lock();
> +	mutex_lock(&rdtgroup_mutex);
> +
> +	if (!resctrl_arch_get_io_alloc_enabled(r)) {
> +		rdt_last_cmd_puts("io_alloc feature is not enabled\n");
> +		ret = -EINVAL;
> +		goto cbm_show_out;
> +	}
> +
> +	io_alloc_closid = resctrl_io_alloc_closid_get(r, s);
> +
> +	show_doms(seq, s, io_alloc_closid);
> +
> +cbm_show_out:
> +	mutex_unlock(&rdtgroup_mutex);
> +	cpus_read_unlock();
> +	return ret;
> +}
> +
>  /* rdtgroup information files for one cache resource. */
>  static struct rftype res_common_files[] = {
>  	{
> @@ -2126,6 +2158,12 @@ static struct rftype res_common_files[] = {
>  		.seq_show	= resctrl_io_alloc_show,
>  		.write		= resctrl_io_alloc_write,
>  	},
> +	{
> +		.name		= "io_alloc_cbm",
> +		.mode		= 0444,
> +		.kf_ops		= &rdtgroup_kf_single_ops,
> +		.seq_show	= resctrl_io_alloc_cbm_show,
> +	},
>  	{
>  		.name		= "mba_MBps_event",
>  		.mode		= 0644,

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