linux-kernel - [PATCH v6 09/22] x86/resctrl: Introduce MBM counters bitmap

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Message-ID: <2bdc7920f9dfc24994fe280649cf26dc566a7a90.1722981659.git.babu.moger@amd.com>
Date: Tue, 6 Aug 2024 17:00:46 -0500
From: Babu Moger <babu.moger@....com>
To: <corbet@....net>, <fenghua.yu@...el.com>, <reinette.chatre@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
	<rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
	<yanjiewtw@...il.com>, <babu.moger@....com>, <kim.phillips@....com>,
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	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>, <james.morse@....com>
Subject: [PATCH v6 09/22] x86/resctrl: Introduce MBM counters bitmap

Hardware provides a set of counters when mbm_cntr_assignable feature is
supported. These counters are used for assigning the events in resctrl
group when the feature is enabled.

Introduce mbm_cntrs_free_map bitmap to track available and free counters
and set of routines to allocate and free the counters.

Signed-off-by: Babu Moger <babu.moger@....com>
---
v6: Removed the variable mbm_cntrs_free_map_len. This is not required.
    Removed the call mbm_cntrs_init() in arch code. This needs to be
    done at higher level.
    Used DECLARE_BITMAP to initialize mbm_cntrs_free_map.
    Moved all the counter interfaces mbm_cntr_alloc() and mbm_cntr_free()
    in here as part of separating arch and fs bits.

v5:
   Updated the comments and commit log.
   Few renames
    num_cntrs_free_map -> mbm_cntrs_free_map
    num_cntrs_init -> mbm_cntrs_init
    Added initialization in rdt_get_tree because the default ABMC
    enablement happens during the init.

v4: Changed the name to num_cntrs where applicable.
     Used bitmap apis.
     Added more comments for the globals.

v3: Changed the bitmap name to assign_cntrs_free_map. Removed abmc
     from the name.

v2: Changed the bitmap name to assignable_counter_free_map from
     abmc_counter_free_map.
---
 arch/x86/kernel/cpu/resctrl/internal.h |  2 ++
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 33 ++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 154983a67646..6263362496a3 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -662,6 +662,8 @@ void __check_limbo(struct rdt_mon_domain *d, bool force_free);
 void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
 void __init resctrl_file_fflags_init(const char *config,
 				     unsigned long fflags);
+int mbm_cntr_alloc(struct rdt_resource *r);
+void mbm_cntr_free(u32 cntr_id);
 void rdt_staged_configs_clear(void);
 bool closid_allocated(unsigned int closid);
 int resctrl_find_cleanest_closid(void);
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index ab4fab3b7cf1..c818965e36c9 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -185,6 +185,37 @@ bool closid_allocated(unsigned int closid)
 	return !test_bit(closid, &closid_free_map);
 }
 
+/*
+ * Counter bitmap for tracking the available counters.
+ * ABMC feature provides set of hardware counters for enabling events.
+ * Each event takes one hardware counter. Kernel needs to keep track
+ * of number of available counters.
+ */
+static DECLARE_BITMAP(mbm_cntrs_free_map, 64);
+
+static void mbm_cntrs_init(struct rdt_resource *r)
+{
+	bitmap_fill(mbm_cntrs_free_map, r->mon.num_mbm_cntrs);
+}
+
+int mbm_cntr_alloc(struct rdt_resource *r)
+{
+	int cntr_id;
+
+	cntr_id = find_first_bit(mbm_cntrs_free_map, r->mon.num_mbm_cntrs);
+	if (cntr_id >= r->mon.num_mbm_cntrs)
+		return -ENOSPC;
+
+	__clear_bit(cntr_id, mbm_cntrs_free_map);
+
+	return cntr_id;
+}
+
+void mbm_cntr_free(u32 cntr_id)
+{
+	__set_bit(cntr_id, mbm_cntrs_free_map);
+}
+
 /**
  * rdtgroup_mode_by_closid - Return mode of resource group with closid
  * @closid: closid if the resource group
@@ -2748,6 +2779,8 @@ static int rdt_get_tree(struct fs_context *fc)
 
 	closid_init();
 
+	mbm_cntrs_init(&rdt_resources_all[RDT_RESOURCE_L3].r_resctrl);
+
 	if (resctrl_arch_mon_capable())
 		flags |= RFTYPE_MON;
 
-- 
2.34.1