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fs/resctrl: Disable BMEC event configuration when mbm_event mode is enabled

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The BMEC (Bandwidth Monitoring Event Configuration) feature enables per-domain
event configuration. With BMEC the MBM events are configured using the
mbm_total_bytes_config or mbm_local_bytes_config files in

  /sys/fs/resctrl/info/L3_MON/

and the per-domain event configuration affects all monitor resource groups.

The mbm_event counter assignment mode enables counters to be assigned to RMID
(i.e. a monitor resource group), event pairs, with potentially unique event
configurations associated with every counter.

There may be systems that support both BMEC and mbm_event counter assignment
mode, but resctrl supporting both concurrently will present a conflicting
interface to the user with both per-domain and per RMID, event configurations
active at the same time.

The mbm_event counter assignment provides most flexibility to user space
and aligns with Arm's counter support. On systems that support both,
disable BMEC event configuration when mbm_event mode is enabled by hiding
the mbm_total_bytes_config or mbm_local_bytes_config files when mbm_event
mode is enabled. Ensure mon_features always displays accurate information
about monitor features.

Suggested-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/cover.1757108044.git.babu.moger@amd.com
This commit is contained in:
Babu Moger
2025-09-05 16:34:29 -05:00
committed by Borislav Petkov (AMD)
parent 88bee79640
commit 9f0209b857
1 changed files with 46 additions and 1 deletions
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47
fs/resctrl/rdtgroup.c
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@@ -1150,7 +1150,8 @@ static int rdt_mon_features_show(struct kernfs_open_file *of,
if (mevt->rid != r->rid || !mevt->enabled)
continue;
seq_printf(seq, "%s\n", mevt->name);
if (mevt->configurable)
if (mevt->configurable &&
!resctrl_arch_mbm_cntr_assign_enabled(r))
seq_printf(seq, "%s_config\n", mevt->name);
}
@@ -1799,6 +1800,44 @@ static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
return ret ?: nbytes;
}
/*
* resctrl_bmec_files_show() — Controls the visibility of BMEC-related resctrl
* files. When @show is true, the files are displayed; when false, the files
* are hidden.
* Don't treat kernfs_find_and_get failure as an error, since this function may
* be called regardless of whether BMEC is supported or the event is enabled.
*/
static void resctrl_bmec_files_show(struct rdt_resource *r, struct kernfs_node *l3_mon_kn,
bool show)
{
struct kernfs_node *kn_config, *mon_kn = NULL;
char name[32];
if (!l3_mon_kn) {
sprintf(name, "%s_MON", r->name);
mon_kn = kernfs_find_and_get(kn_info, name);
if (!mon_kn)
return;
l3_mon_kn = mon_kn;
}
kn_config = kernfs_find_and_get(l3_mon_kn, "mbm_total_bytes_config");
if (kn_config) {
kernfs_show(kn_config, show);
kernfs_put(kn_config);
}
kn_config = kernfs_find_and_get(l3_mon_kn, "mbm_local_bytes_config");
if (kn_config) {
kernfs_show(kn_config, show);
kernfs_put(kn_config);
}
/* Release the reference only if it was acquired */
if (mon_kn)
kernfs_put(mon_kn);
}
/* rdtgroup information files for one cache resource. */
static struct rftype res_common_files[] = {
{
@@ -2267,6 +2306,12 @@ static int rdtgroup_mkdir_info_resdir(void *priv, char *name,
ret = resctrl_mkdir_event_configs(r, kn_subdir);
if (ret)
return ret;
/*
* Hide BMEC related files if mbm_event mode
* is enabled.
*/
if (resctrl_arch_mbm_cntr_assign_enabled(r))
resctrl_bmec_files_show(r, kn_subdir, false);
}
}