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

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

Hi Reinette,

On 3/21/25 17:58, Reinette Chatre wrote:
> 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"?

Yes. That is correct.


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

Sure.

> 
>> +		return -EINVAL;
> 
> How about ENODEV?

Sure.

> 
>> +	}
>> +
>> +	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,
> 
> Reinette
> 

-- 
Thanks
Babu Moger