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Date:   Tue, 22 Nov 2022 16:19:48 -0800
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Subject: Re: [PATCH v8 08/13] x86/resctrl: Add sysfs interface to read
 mbm_total_bytes_config
Content-Language: en-US
To:     Babu Moger <babu.moger@amd.com>, <corbet@lwn.net>,
        <tglx@linutronix.de>, <mingo@redhat.com>, <bp@alien8.de>
CC:     <fenghua.yu@intel.com>, <dave.hansen@linux.intel.com>,
        <x86@kernel.org>, <hpa@zytor.com>, <paulmck@kernel.org>,
        <akpm@linux-foundation.org>, <quic_neeraju@quicinc.com>,
        <rdunlap@infradead.org>, <damien.lemoal@opensource.wdc.com>,
        <songmuchun@bytedance.com>, <peterz@infradead.org>,
        <jpoimboe@kernel.org>, <pbonzini@redhat.com>,
        <chang.seok.bae@intel.com>, <pawan.kumar.gupta@linux.intel.com>,
        <jmattson@google.com>, <daniel.sneddon@linux.intel.com>,
        <sandipan.das@amd.com>, <tony.luck@intel.com>,
        <james.morse@arm.com>, <linux-doc@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <bagasdotme@gmail.com>,
        <eranian@google.com>
References: <166759188265.3281208.11769277079826754455.stgit@bmoger-ubuntu>
 <166759205510.3281208.11437041392524040365.stgit@bmoger-ubuntu>
From:   Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <166759205510.3281208.11437041392524040365.stgit@bmoger-ubuntu>
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Hi Babu,

On 11/4/2022 1:00 PM, Babu Moger wrote:
> The current event configuration can be viewed by the user by reading
> the configuration file /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config.
> The event configuration settings are domain specific and will affect all
> the CPUs in the domain.
> 
> 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
> ====  ===========================================================
> 
> By default, the mbm_total_bytes_config is set to 0x7f to count all the
> event types.
> 
> For example:
>     $cat /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config
>     0=0x7f;1=0x7f;2=0x7f;3=0x7f
> 
>     In this case, the event mbm_total_bytes is currently configured
>     with 0x7f on domains 0 to 3.
> 
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
>  arch/x86/kernel/cpu/resctrl/internal.h |   28 ++++++++++
>  arch/x86/kernel/cpu/resctrl/monitor.c  |    1 
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c |   87 ++++++++++++++++++++++++++++++++
>  3 files changed, 116 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 5459b5022760..c74285fd0f6e 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
> @@ -41,6 +42,32 @@
>   */
>  #define MBM_CNTR_WIDTH_OFFSET_MAX (62 - MBM_CNTR_WIDTH_BASE)
>  
> +/* Reads to Local DRAM Memory */
> +#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)
> +
> +/* Max event bits supported */
> +#define MAX_EVT_CONFIG_BITS		GENMASK(6, 0)
> +
> +/* Max configurable events */
> +#define MAX_CONFIG_EVENTS		2
>  

This max being disconnected from what it is a max of looks like
a source of future confusion.

>  struct rdt_fs_context {
>  	struct kernfs_fs_context	kfc;
> @@ -542,5 +569,6 @@ bool has_busy_rmid(struct rdt_resource *r, struct rdt_domain *d);
>  void __check_limbo(struct rdt_domain *d, bool force_free);
>  void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
>  void __init thread_throttle_mode_init(void);
> +void mbm_config_rftype_init(void);
>  
>  #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 06c2dc980855..a188dacab6c8 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -787,6 +787,7 @@ int rdt_get_mon_l3_config(struct rdt_resource *r)
>  	if (mon_configurable) {
>  		mbm_total_event.configurable = true;
>  		mbm_local_event.configurable = true;
> +		mbm_config_rftype_init();
>  	}
>  
>  	l3_mon_evt_init(r);
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 8342feb54a7f..dea58b6b4aa4 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1423,6 +1423,78 @@ static int rdtgroup_size_show(struct kernfs_open_file *of,
>  	return ret;
>  }
>  
> +struct mon_config_info {
> +	u32 evtid;
> +	u32 mon_config;
> +};
> +
> +/**
> + * mon_event_config_index_get - get the index for the configurable event
> + * @evtid: event id.
> + *
> + * Return: 0 for evtid == QOS_L3_MBM_TOTAL_EVENT_ID
> + *         1 for evtid == QOS_L3_MBM_LOCAL_EVENT_ID
> + *         > 1 otherwise
> + */
> +static inline unsigned int mon_event_config_index_get(u32 evtid)
> +{
> +	return evtid - QOS_L3_MBM_TOTAL_EVENT_ID;
> +}

It seems strange that the validation of the index is split
from where the index is determined. I think it would be easier
to understand, and reduce code duplication, it if is done together.

How about:
#define INVALID_CONFIG_INDEX   UINT_MAX

static inline unsigned int mon_event_config_index_get(u32 evtid)
{
	switch (evtid) {
	case QOS_L3_MBM_TOTAL_EVENT_ID:
		return 0;
	case QOS_L3_MBM_LOCAL_EVENT_ID:
		return 1;
	default:
		/* WARN */
		return INVALID_CONFIG_INDEX;
	}
}

What do you think?

> +
> +static void mon_event_config_read(void *info)
> +{
> +	struct mon_config_info *mon_info = info;
> +	u32 h, index;
> +
> +	index = mon_event_config_index_get(mon_info->evtid);
> +	if (index >= MAX_CONFIG_EVENTS) {
> +		pr_warn_once("Invalid event id %d\n", mon_info->evtid);
> +		return;
> +	}
> +	rdmsr(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config, h);
> +}
> +
> +static 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);
> +}
> +
> +static int mbm_config_show(struct seq_file *s, struct rdt_resource *r, u32 evtid)
> +{
> +	struct mon_config_info mon_info = {0};

> +	struct rdt_domain *dom;
> +	bool sep = false;
> +
> +	mutex_lock(&rdtgroup_mutex);
> +
> +	list_for_each_entry(dom, &r->domains, list) {
> +		if (sep)
> +			seq_puts(s, ";");
> +
> +		mon_info.evtid = evtid;
> +		mondata_config_read(dom, &mon_info);
> +
> +		seq_printf(s, "%d=0x%02lx", dom->id,

This is a u32 ... is just x sufficient?

> +			   mon_info.mon_config & MAX_EVT_CONFIG_BITS);

Please do this masking within mondata_config_read(). It should
not be required for every mon_config_read() caller to validate the
data because they may forget (re. patch 10).

> +		sep = true;
> +	}
> +	seq_puts(s, "\n");
> +
> +	mutex_unlock(&rdtgroup_mutex);
> +
> +	return 0;
> +}
> +
> +static int mbm_total_bytes_config_show(struct kernfs_open_file *of,
> +				       struct seq_file *seq, void *v)
> +{
> +	struct rdt_resource *r = of->kn->parent->priv;
> +
> +	mbm_config_show(seq, r, QOS_L3_MBM_TOTAL_EVENT_ID);
> +
> +	return 0;
> +}
> +
>  /* rdtgroup information files for one cache resource. */
>  static struct rftype res_common_files[] = {
>  	{
> @@ -1521,6 +1593,12 @@ static struct rftype res_common_files[] = {
>  		.seq_show	= max_threshold_occ_show,
>  		.fflags		= RF_MON_INFO | RFTYPE_RES_CACHE,
>  	},
> +	{
> +		.name		= "mbm_total_bytes_config",
> +		.mode		= 0444,
> +		.kf_ops		= &rdtgroup_kf_single_ops,
> +		.seq_show	= mbm_total_bytes_config_show,
> +	},
>  	{
>  		.name		= "cpus",
>  		.mode		= 0644,
> @@ -1627,6 +1705,15 @@ void __init thread_throttle_mode_init(void)
>  	rft->fflags = RF_CTRL_INFO | RFTYPE_RES_MB;
>  }
>  
> +void mbm_config_rftype_init(void)

Does this need __init?

> +{
> +	struct rftype *rft;
> +
> +	rft = rdtgroup_get_rftype_by_name("mbm_total_bytes_config");
> +	if (rft)
> +		rft->fflags = RF_MON_INFO | RFTYPE_RES_CACHE;
> +}
> +
>  /**
>   * rdtgroup_kn_mode_restrict - Restrict user access to named resctrl file
>   * @r: The resource group with which the file is associated.
> 
> 

Reinette