Re: [PATCH v4 10/13] x86/resctrl: Add the sysfs interface to read the event configuration

[Reinette Chatre]

Hi Babu,

On 9/7/2022 11:01 AM, Babu Moger wrote:
> The current event configuration can be viewed by the user by reading
> the sysfs configuration file.
> 
> Following are the types of events supported:
> 
> ====  ===========================================================
> Bits   Description
> ====  ===========================================================
> 6      Dirty Victims from the QOS domain to all types of memory
> 5      Reads to slow memory in the non-local NUMA domain
> 4      Reads to slow memory in the local NUMA domain
> 3      Non-temporal writes to non-local NUMA domain
> 2      Non-temporal writes to local NUMA domain
> 1      Reads to memory in the non-local NUMA domain
> 0      Reads to memory in the local NUMA domain
> ====  ===========================================================
> 

...

> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 45923eb4022f..96f439324d78 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -15,6 +15,7 @@
>  #define MSR_IA32_MBA_THRTL_BASE		0xd50
>  #define MSR_IA32_MBA_BW_BASE		0xc0000200
>  #define MSR_IA32_SMBA_BW_BASE		0xc0000280
> +#define MSR_IA32_EVT_CFG_BASE		0xc0000400
>  
>  #define MSR_IA32_QM_CTR			0x0c8e
>  #define MSR_IA32_QM_EVTSEL		0x0c8d
> @@ -50,6 +51,29 @@
>   */
>  #define MBM_CNTR_WIDTH_OFFSET_MAX (62 - MBM_CNTR_WIDTH_BASE)
>  
> +/* Reads to Local DRAM Memory */

What prompted the terminology switch between the
changelog ("local NUMA")  and the comments ("DRAM")?

> +#define READS_TO_LOCAL_MEM		BIT(0)
> +
> +/* Reads to Remote DRAM Memory */
> +#define READS_TO_REMOTE_MEM		BIT(1)
> +
> +/* Non-Temporal Writes to Local Memory */
> +#define NON_TEMP_WRITE_TO_LOCAL_MEM	BIT(2)
> +
> +/* Non-Temporal Writes to Remote Memory */
> +#define NON_TEMP_WRITE_TO_REMOTE_MEM	BIT(3)
> +
> +/* Reads to Local Memory the system identifies as "Slow Memory" */
> +#define READS_TO_LOCAL_S_MEM		BIT(4)
> +
> +/* Reads to Remote Memory the system identifies as "Slow Memory" */
> +#define READS_TO_REMOTE_S_MEM		BIT(5)
> +
> +/* Dirty Victims to All Types of Memory */
> +#define  DIRTY_VICTIMS_TO_ALL_MEM	BIT(6)
> +

Could you please fixup the comments to only capitalize 
the first word of each sentence (unless it is an acronym
or required for some other reason)?

> +/* Max event bits supported */
> +#define MAX_EVT_CONFIG_BITS		GENMASK(6, 0)
>  
>  struct rdt_fs_context {
>  	struct kernfs_fs_context	kfc;
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index da11fdad204d..6f067c1ac7c1 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -254,8 +254,85 @@ static const struct kernfs_ops kf_mondata_ops = {
>  	.seq_show		= rdtgroup_mondata_show,
>  };
>  
> +struct mon_config_info {
> +	u32 evtid;
> +	u32 mon_config;
> +};
> +
> +/*
> + * This is called via IPI to read the CQM/MBM counters
> + * in a domain.

This comment does not seem accurate - it is not reading the
actual counters but the configuration of the counters?

> + */
> +void mon_event_config_read(void *info)
> +{
> +	struct mon_config_info *mon_info = info;
> +	u32 h, msr_index;
> +
> +	switch (mon_info->evtid) {
> +	case QOS_L3_MBM_TOTAL_EVENT_ID:
> +		msr_index = 0;
> +		break;
> +	case QOS_L3_MBM_LOCAL_EVENT_ID:
> +		msr_index = 1;
> +		break;
> +	default:
> +		/* Not expected to come here */
> +		return;
> +	}
> +
> +	rdmsr(MSR_IA32_EVT_CFG_BASE + msr_index, mon_info->mon_config, h);
> +}
> +
> +void mondata_config_read(struct rdt_domain *d, struct mon_config_info *mon_info)
> +{
> +	smp_call_function_any(&d->cpu_mask, mon_event_config_read, mon_info, 1);
> +}
> +
> +int rdtgroup_mondata_config_show(struct seq_file *m, void *arg)
> +{
> +	struct kernfs_open_file *of = m->private;
> +	struct mon_config_info mon_info;

Could you please initialize this struct? I think this is important considering
that there is an (albeit unlikely) chance that uninitialized data can be returned
to user space.

> +	struct rdt_hw_resource *hw_res;
> +	u32 resid, evtid, domid;
> +	struct rdtgroup *rdtgrp;
> +	struct rdt_resource *r;
> +	union mon_data_bits md;
> +	struct rdt_domain *d;
> +	int ret = 0;
> +
> +	rdtgrp = rdtgroup_kn_lock_live(of->kn);
> +	if (!rdtgrp) {
> +		ret = -ENOENT;
> +		goto out;
> +	}
> +
> +	md.priv = of->kn->priv;
> +	resid = md.u.rid;
> +	domid = md.u.domid;
> +	evtid = md.u.evtid;
> +
> +	hw_res = &rdt_resources_all[resid];
> +	r = &hw_res->r_resctrl;
> +
> +	d = rdt_find_domain(r, domid, NULL);
> +	if (IS_ERR_OR_NULL(d)) {
> +		ret = -ENOENT;
> +		goto out;
> +	}
> +
> +	mon_info.evtid = evtid;
> +	mondata_config_read(d, &mon_info);
> +
> +	seq_printf(m, "0x%x\n", mon_info.mon_config);
> +
> +out:
> +	rdtgroup_kn_unlock(of->kn);
> +	return ret;
> +}
> +
>  static const struct kernfs_ops kf_mondata_config_ops = {
>  	.atomic_write_len       = PAGE_SIZE,
> +	.seq_show               = rdtgroup_mondata_config_show,
>  };
  
>  static bool is_cpu_list(struct kernfs_open_file *of)
> 
> 

Reinette