[PATCH v1 9/9] x86/resctrl: Add mount option to enable soft RMID

Peter Newman
2023-04-21T14:19:10Z

Add the 'mbm_soft_rmid' mount option to enable soft RMIDs.

This requires adding a mechanism for disabling a monitoring event at
mount time to prevent the llc_occupancy event from being presented to
the user.

Signed-off-by: Peter Newman <peternewman@google.com>
---
arch/x86/kernel/cpu/resctrl/internal.h | 3 ++
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 51 ++++++++++++++++++++++++++
2 files changed, 54 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index e6ff31a4dbc4..604e3d550601 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -59,6 +59,7 @@ struct rdt_fs_context {
bool enable_cdpl2;
bool enable_cdpl3;
bool enable_mba_mbps;
+ bool enable_mbm_soft_rmid;
};

static inline struct rdt_fs_context *rdt_fc2context(struct fs_context *fc)
@@ -76,12 +77,14 @@ DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
* @evtid: event id
* @name: name of the event
* @configurable: true if the event is configurable
+ * @enabled: true if event is disabled
* @list: entry in &rdt_resource->evt_list
*/
struct mon_evt {
enum resctrl_event_id evtid;
char *name;
bool configurable;
+ bool disabled;
struct list_head list;
};

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index c10f4798156a..c2abf69c2dcf 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1013,6 +1013,8 @@ static int rdt_mon_features_show(struct kernfs_open_file *of,
struct mon_evt *mevt;

list_for_each_entry(mevt, &r->evt_list, list) {
+ if (mevt->disabled)
+ continue;
seq_printf(seq, "%s\n", mevt->name);
if (mevt->configurable)
seq_printf(seq, "%s_config\n", mevt->name);
@@ -2204,6 +2206,37 @@ static bool supports_mba_mbps(void)
r->alloc_capable && is_mba_linear());
}

+static bool supports_mbm_soft_rmid(void)
+{
+ return is_mbm_enabled();
+}
+
+int set_mbm_soft_rmid(bool mbm_soft_rmid)
+{
+ struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
+ struct mon_evt *mevt = NULL;
+
+ /*
+ * is_llc_occupancy_enabled() will always return false when disabling,
+ * so search for the llc_occupancy event unconditionally.
+ */
+ list_for_each_entry(mevt, &r->evt_list, list) {
+ if (strcmp(mevt->name, "llc_occupancy") == 0) {
+ mevt->disabled = mbm_soft_rmid;
+ break;
+ }
+ }
+
+ rdt_mon_soft_rmid = mbm_soft_rmid;
+
+ if (mbm_soft_rmid)
+ static_branch_enable_cpuslocked(&rdt_soft_rmid_enable_key);
+ else
+ static_branch_disable_cpuslocked(&rdt_soft_rmid_enable_key);
+
+ return 0;
+}
+
/*
* Enable or disable the MBA software controller
* which helps user specify bandwidth in MBps.
@@ -2359,6 +2392,9 @@ static int rdt_enable_ctx(struct rdt_fs_context *ctx)
if (!ret && ctx->enable_mba_mbps)
ret = set_mba_sc(true);

+ if (!ret && ctx->enable_mbm_soft_rmid)
+ ret = set_mbm_soft_rmid(true);
+
return ret;
}

@@ -2534,6 +2570,8 @@ static int rdt_get_tree(struct fs_context *fc)
out_mba:
if (ctx->enable_mba_mbps)
set_mba_sc(false);
+ if (ctx->enable_mbm_soft_rmid)
+ set_mbm_soft_rmid(false);
out_cdp:
cdp_disable_all();
out:
@@ -2547,6 +2585,7 @@ enum rdt_param {
Opt_cdp,
Opt_cdpl2,
Opt_mba_mbps,
+ Opt_mbm_soft_rmid,
nr__rdt_params
};

@@ -2554,6 +2593,7 @@ static const struct fs_parameter_spec rdt_fs_parameters[] = {
fsparam_flag("cdp", Opt_cdp),
fsparam_flag("cdpl2", Opt_cdpl2),
fsparam_flag("mba_MBps", Opt_mba_mbps),
+ fsparam_flag("mbm_soft_rmid", Opt_mbm_soft_rmid),
{}
};

@@ -2579,6 +2619,11 @@ static int rdt_parse_param(struct fs_context *fc, struct fs_parameter *param)
return -EINVAL;
ctx->enable_mba_mbps = true;
return 0;
+ case Opt_mbm_soft_rmid:
+ if (!supports_mbm_soft_rmid())
+ return -EINVAL;
+ ctx->enable_mbm_soft_rmid = true;
+ return 0;
}

return -EINVAL;
@@ -2767,6 +2812,7 @@ static void rdt_kill_sb(struct super_block *sb)
cpus_read_lock();
mutex_lock(&rdtgroup_mutex);

+ set_mbm_soft_rmid(false);
set_mba_sc(false);

/*Put everything back to default values. */
@@ -2861,6 +2907,8 @@ static int mkdir_mondata_subdir(struct kernfs_node *parent_kn,
priv.u.rid = r->rid;
priv.u.domid = d->id;
list_for_each_entry(mevt, &r->evt_list, list) {
+ if (mevt->disabled)
+ continue;
priv.u.evtid = mevt->evtid;
ret = mon_addfile(kn, mevt->name, priv.priv);
if (ret)
@@ -3517,6 +3565,9 @@ static int rdtgroup_show_options(struct seq_file *seq, struct kernfs_root *kf)
if (is_mba_sc(&rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl))
seq_puts(seq, ",mba_MBps");

+ if (static_branch_likely(&rdt_soft_rmid_enable_key))
+ seq_puts(seq, ",mbm_soft_rmid");
+
return 0;
}

--
2.40.0.634.g4ca3ef3211-goog