[PATCH v12 02/26] x86/resctrl: Remove MSR reading of event configuration value

From: Babu Moger
Date: Thu Apr 03 2025 - 20:35:07 EST

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The event configuration is domain specific and initialized during domain
initialization. The values are stored in struct rdt_hw_mon_domain.

It is not required to read the configuration register every time user asks
for it. Use the value stored in struct rdt_hw_mon_domain instead.

Introduce resctrl_arch_mon_event_config_get() and
resctrl_arch_mon_event_config_set() to get/set architecture domain specific
mbm_total_cfg/mbm_local_cfg values.

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v12: Removed the un-necessary initialization of mon_config_info structure.
Changed wrmsrl instead of wrmsr to address the below comment.
https://lore.kernel.org/lkml/0fc8dbd4-07d8-40bd-8eec-402b48762807@xxxxxxxxx/
Fixed a minor typo in comment.
Added comments to resctrl_arch_mon_event_config_get() and resctrl_arch_mon_event_config_set()
Resolved the conflicts from the recent changes.
This patch is for BMEC and there is no dependancy on ABMC feature. Moved it earlier.

v11: Moved the mon_config_info structure definition to internal.h.
Moved resctrl_arch_mon_event_config_get() and resctrl_arch_mon_event_config_set()
to monitor.c file.
Renamed local variable from val to config_val.

v10: Moved the mon_config_info structure definition to resctrl.h.

v9: Removed QOS_L3_OCCUP_EVENT_ID switch case in resctrl_arch_mon_event_config_set.
Fixed a unnecessary space.

v8: Renamed
resctrl_arch_event_config_get() to resctrl_arch_mon_event_config_get().
resctrl_arch_event_config_set() to resctrl_arch_mon_event_config_set().

v7: Removed check if (val == INVALID_CONFIG_VALUE) as resctrl_arch_event_config_get
already prints warning.
Kept the Event config value definitions as is.

v6: Fixed inconstancy with types. Made all the types to u32 for config
value.
Removed few rdt_last_cmd_puts as it is not necessary.
Removed unused config value definitions.
Few more updates to commit message.

v5: Introduced resctrl_arch_event_config_get and
resctrl_arch_event_config_get() based on our discussion.
https://lore.kernel.org/lkml/68e861f9-245d-4496-a72e-46fc57d19c62@xxxxxxx/

v4: New patch.
---
arch/x86/kernel/cpu/resctrl/monitor.c | 52 +++++++++++++++++++++
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 63 +++++---------------------
include/linux/resctrl.h | 18 +++-----
3 files changed, 71 insertions(+), 62 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index abd337fbd01d..b84cd48c3d95 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -1330,3 +1330,55 @@ void __init intel_rdt_mbm_apply_quirk(void)
mbm_cf_rmidthreshold = mbm_cf_table[cf_index].rmidthreshold;
mbm_cf = mbm_cf_table[cf_index].cf;
}
+
+/*
+ * May run on CPU that does not belong to domain.
+ */
+u32 resctrl_arch_mon_event_config_get(struct rdt_mon_domain *d,
+ enum resctrl_event_id eventid)
+{
+ struct rdt_hw_mon_domain *hw_dom = resctrl_to_arch_mon_dom(d);
+
+ switch (eventid) {
+ case QOS_L3_OCCUP_EVENT_ID:
+ break;
+ case QOS_L3_MBM_TOTAL_EVENT_ID:
+ return hw_dom->mbm_total_cfg;
+ case QOS_L3_MBM_LOCAL_EVENT_ID:
+ return hw_dom->mbm_local_cfg;
+ }
+
+ /* Never expect to get here */
+ WARN_ON_ONCE(1);
+
+ return INVALID_CONFIG_VALUE;
+}
+
+/*
+ * Runs on CPU that belongs to domain.
+ */
+void resctrl_arch_mon_event_config_set(void *info)
+{
+ struct resctrl_mon_config_info *mon_info = info;
+ struct rdt_hw_mon_domain *hw_dom;
+ unsigned int index;
+
+ index = mon_event_config_index_get(mon_info->evtid);
+ if (index == INVALID_CONFIG_INDEX)
+ return;
+
+ wrmsrl(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config);
+
+ hw_dom = resctrl_to_arch_mon_dom(mon_info->d);
+
+ switch (mon_info->evtid) {
+ case QOS_L3_MBM_TOTAL_EVENT_ID:
+ hw_dom->mbm_total_cfg = mon_info->mon_config;
+ break;
+ case QOS_L3_MBM_LOCAL_EVENT_ID:
+ hw_dom->mbm_local_cfg = mon_info->mon_config;
+ break;
+ default:
+ break;
+ }
+}
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index bee32eaef8ab..b8100c89f1a6 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1614,34 +1614,11 @@ unsigned int mon_event_config_index_get(u32 evtid)
}
}

-void resctrl_arch_mon_event_config_read(void *_config_info)
-{
- struct resctrl_mon_config_info *config_info = _config_info;
- unsigned int index;
- u64 msrval;
-
- index = mon_event_config_index_get(config_info->evtid);
- if (index == INVALID_CONFIG_INDEX) {
- pr_warn_once("Invalid event id %d\n", config_info->evtid);
- return;
- }
- rdmsrl(MSR_IA32_EVT_CFG_BASE + index, msrval);
-
- /* Report only the valid event configuration bits */
- config_info->mon_config = msrval & MAX_EVT_CONFIG_BITS;
-}
-
-static void mondata_config_read(struct resctrl_mon_config_info *mon_info)
-{
- smp_call_function_any(&mon_info->d->hdr.cpu_mask,
- resctrl_arch_mon_event_config_read, mon_info, 1);
-}
-
static int mbm_config_show(struct seq_file *s, struct rdt_resource *r, u32 evtid)
{
- struct resctrl_mon_config_info mon_info;
struct rdt_mon_domain *dom;
bool sep = false;
+ u32 config_val;

cpus_read_lock();
mutex_lock(&rdtgroup_mutex);
@@ -1650,13 +1627,8 @@ static int mbm_config_show(struct seq_file *s, struct rdt_resource *r, u32 evtid
if (sep)
seq_puts(s, ";");

- memset(&mon_info, 0, sizeof(struct resctrl_mon_config_info));
- mon_info.r = r;
- mon_info.d = dom;
- mon_info.evtid = evtid;
- mondata_config_read(&mon_info);
-
- seq_printf(s, "%d=0x%02x", dom->hdr.id, mon_info.mon_config);
+ config_val = resctrl_arch_mon_event_config_get(dom, evtid);
+ seq_printf(s, "%d=0x%02x", dom->hdr.id, config_val);
sep = true;
}
seq_puts(s, "\n");
@@ -1687,35 +1659,23 @@ static int mbm_local_bytes_config_show(struct kernfs_open_file *of,
return 0;
}

-void resctrl_arch_mon_event_config_write(void *_config_info)
-{
- struct resctrl_mon_config_info *config_info = _config_info;
- unsigned int index;
-
- index = mon_event_config_index_get(config_info->evtid);
- if (index == INVALID_CONFIG_INDEX) {
- pr_warn_once("Invalid event id %d\n", config_info->evtid);
- return;
- }
- wrmsr(MSR_IA32_EVT_CFG_BASE + index, config_info->mon_config, 0);
-}
-
static void mbm_config_write_domain(struct rdt_resource *r,
struct rdt_mon_domain *d, u32 evtid, u32 val)
{
- struct resctrl_mon_config_info mon_info = {0};
+ struct resctrl_mon_config_info mon_info;
+ u32 config_val;

/*
- * Read the current config value first. If both are the same then
+ * Check the current config value first. If both are the same then
* no need to write it again.
*/
+ config_val = resctrl_arch_mon_event_config_get(d, evtid);
+ if (config_val == INVALID_CONFIG_VALUE || config_val == val)
+ return;
+
mon_info.r = r;
mon_info.d = d;
mon_info.evtid = evtid;
- mondata_config_read(&mon_info);
- if (mon_info.mon_config == val)
- return;
-
mon_info.mon_config = val;

/*
@@ -1724,7 +1684,8 @@ static void mbm_config_write_domain(struct rdt_resource *r,
* are scoped at the domain level. Writing any of these MSRs
* on one CPU is observed by all the CPUs in the domain.
*/
- smp_call_function_any(&d->hdr.cpu_mask, resctrl_arch_mon_event_config_write,
+ smp_call_function_any(&d->hdr.cpu_mask,
+ resctrl_arch_mon_event_config_set,
&mon_info, 1);

/*
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 880351ca3dfc..afa9aabf014c 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -361,7 +361,7 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid);
__init bool resctrl_arch_is_evt_configurable(enum resctrl_event_id evt);

/**
- * resctrl_arch_mon_event_config_write() - Write the config for an event.
+ * resctrl_arch_mon_event_config_set() - Write the config for an event.
* @config_info: struct resctrl_mon_config_info describing the resource, domain
* and event.
*
@@ -370,19 +370,15 @@ __init bool resctrl_arch_is_evt_configurable(enum resctrl_event_id evt);
*
* Called via IPI to reach a CPU that is a member of the specified domain.
*/
-void resctrl_arch_mon_event_config_write(void *config_info);
+void resctrl_arch_mon_event_config_set(void *config_info);

/**
- * resctrl_arch_mon_event_config_read() - Read the config for an event.
- * @config_info: struct resctrl_mon_config_info describing the resource, domain
- * and event.
- *
- * Reads resource, domain and eventid from @config_info and reads the
- * hardware config value into config_info->mon_config.
- *
- * Called via IPI to reach a CPU that is a member of the specified domain.
+ * resctrl_arch_mon_event_config_get() - Get config value from the hardware domain.
+ * @d: Monitoring domain to read config value
+ * @eventid: enum resctrl_event_id describing type
*/
-void resctrl_arch_mon_event_config_read(void *config_info);
+u32 resctrl_arch_mon_event_config_get(struct rdt_mon_domain *d,
+ enum resctrl_event_id eventid);

/* For use by arch code to remap resctrl's smaller CDP CLOSID range */
static inline u32 resctrl_get_config_index(u32 closid,
--
2.34.1

Next message: Babu Moger: "[PATCH v12 15/26] x86/resctrl: Add the functionality to unassign MBM events"
Previous message: Babu Moger: "[PATCH v12 08/26] x86/resctrl: Introduce the interface to display monitor mode"
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Next in thread: Babu Moger: "[PATCH v12 15/26] x86/resctrl: Add the functionality to unassign MBM events"
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