[PATCH v2 08/23] x86/resctrl: Create mba_sc configuration in the rdt_domain

[James Morse]

To support resctrl's MBA software controller, the architecture must provide
a second configuration array to hold the mbps_val from user-space.

This complicates the interface between the architecture code.

Make the filesystem parts of resctrl create an array for the mba_sc
values when is_mba_sc() is set to true. The software controller
can be changed to use this, allowing the architecture code to only
consider the values configured in hardware.

Signed-off-by: James Morse <james.morse@xxxxxxx>
---
Changes since v1:
 * Added missing error handling to mba_sc_domain_allocate() in
   domain_setup_mon_state()
 * Added comment about mba_sc_domain_allocate() races
 * Squashed out struct resctrl_mba_sc
 * Moved mount time alloc/free calls to set_mba_sc().
 * Removed mount check in resctrl_offline_domain()
 * Reword commit message
---
 arch/x86/kernel/cpu/resctrl/internal.h |  1 -
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 67 ++++++++++++++++++++++++++
 include/linux/resctrl.h                |  6 +++
 3 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index e12b55f815bf..a7e2cbce29d5 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -36,7 +36,6 @@
 #define MBM_OVERFLOW_INTERVAL		1000
 #define MAX_MBA_BW			100u
 #define MBA_IS_LINEAR			0x4
-#define MBA_MAX_MBPS			U32_MAX
 #define MAX_MBA_BW_AMD			0x800
 #define MBM_CNTR_WIDTH_OFFSET_AMD	20
 
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 38670bb810cb..9d402bc8bdff 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1889,6 +1889,64 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r)
 		l3_qos_cfg_update(&hw_res->cdp_enabled);
 }
 
+static int mba_sc_domain_allocate(struct rdt_resource *r, struct rdt_domain *d)
+{
+	u32 num_closid = resctrl_arch_get_num_closid(r);
+	int cpu = cpumask_any(&d->cpu_mask);
+	int i;
+
+	/*
+	 * d->mbps_val is allocated by a call to this function in set_mba_sc(),
+	 * and domain_setup_mon_state(). Both calls are guarded by is_mba_sc(),
+	 * which can only return true while the filesystem is mounted. The
+	 * two calls are prevented from racing as rdt_get_tree() takes the
+	 * cpuhp read lock before calling rdt_enable_ctx(ctx), which prevents
+	 * it running concurrently with resctrl_online_domain().
+	 */
+	lockdep_assert_cpus_held();
+
+	d->mbps_val = kcalloc_node(num_closid, sizeof(*d->mbps_val),
+				   GFP_KERNEL, cpu_to_node(cpu));
+	if (!d->mbps_val)
+		return -ENOMEM;
+
+	for (i = 0; i < num_closid; i++)
+		d->mbps_val[i] = MBA_MAX_MBPS;
+
+	return 0;
+}
+
+static int mba_sc_allocate(struct rdt_resource *r)
+{
+	struct rdt_domain *d;
+	int ret;
+
+	list_for_each_entry(d, &r->domains, list) {
+		ret = mba_sc_domain_allocate(r, d);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+static void mba_sc_domain_destroy(struct rdt_resource *r,
+				  struct rdt_domain *d)
+{
+	kfree(d->mbps_val);
+	d->mbps_val = NULL;
+}
+
+static void mba_sc_destroy(struct rdt_resource *r)
+{
+	struct rdt_domain *d;
+
+	lockdep_assert_cpus_held();
+
+	list_for_each_entry(d, &r->domains, list)
+		mba_sc_domain_destroy(r, d);
+}
+
 /*
  * Enable or disable the MBA software controller
  * which helps user specify bandwidth in MBps.
@@ -1911,6 +1969,10 @@ static int set_mba_sc(bool mba_sc)
 		setup_default_ctrlval(r, hw_dom->ctrl_val, hw_dom->mbps_val);
 	}
 
+	if (is_mba_sc(r))
+		return mba_sc_allocate(r);
+
+	mba_sc_destroy(r);
 	return 0;
 }
 
@@ -3259,6 +3321,8 @@ void resctrl_offline_domain(struct rdt_resource *r, struct rdt_domain *d)
 		__check_limbo(d, true);
 		cancel_delayed_work(&d->cqm_limbo);
 	}
+	if (is_mba_sc(r))
+		mba_sc_domain_destroy(r, d);
 	bitmap_free(d->rmid_busy_llc);
 	kfree(d->mbm_total);
 	kfree(d->mbm_local);
@@ -3291,6 +3355,9 @@ static int domain_setup_mon_state(struct rdt_resource *r, struct rdt_domain *d)
 		}
 	}
 
+	if (is_mba_sc(r))
+		return mba_sc_domain_allocate(r, d);
+
 	return 0;
 }
 
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 5d283bdd6162..355660d46612 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -15,6 +15,9 @@ int proc_resctrl_show(struct seq_file *m,
 
 #endif
 
+/* max value for struct resctrl_mba_sc's mbps_val */
+#define MBA_MAX_MBPS   U32_MAX
+
 /**
  * enum resctrl_conf_type - The type of configuration.
  * @CDP_NONE:	No prioritisation, both code and data are controlled or monitored.
@@ -53,6 +56,8 @@ struct resctrl_staged_config {
  * @cqm_work_cpu:	worker CPU for CQM h/w counters
  * @plr:		pseudo-locked region (if any) associated with domain
  * @staged_config:	parsed configuration to be applied
+ * @mbps_val:		Array of user specified control values for mba_sc,
+ *			indexed by closid
  */
 struct rdt_domain {
 	struct list_head		list;
@@ -67,6 +72,7 @@ struct rdt_domain {
 	int				cqm_work_cpu;
 	struct pseudo_lock_region	*plr;
 	struct resctrl_staged_config	staged_config[CDP_NUM_TYPES];
+	u32				*mbps_val;
 };
 
 /**
-- 
2.30.2