linux-kernel - [PATCH v13 04/27] x86/resctrl: Detect Assignable Bandwidth Monitoring feature details

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Message-ID: <a4e2388b708883874adcd621f50f773484945489.1747349530.git.babu.moger@amd.com>
Date: Thu, 15 May 2025 17:51:49 -0500
From: Babu Moger <babu.moger@....com>
To: <corbet@....net>, <tony.luck@...el.com>, <reinette.chatre@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
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Subject: [PATCH v13 04/27] x86/resctrl: Detect Assignable Bandwidth Monitoring feature details

ABMC feature details are reported via CPUID Fn8000_0020_EBX_x5.
Bits Description
15:0 MAX_ABMC Maximum Supported Assignable Bandwidth
     Monitoring Counter ID + 1

The feature details are documented in APM listed below [1].
[1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth
Monitoring (ABMC).

Detect the feature and number of assignable monitoring counters supported.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Signed-off-by: Babu Moger <babu.moger@....com>
---
v13: No changes.

v12: Resolved conflicts because of latest merge.
     Removed Reviewed-by as the patch has changed.

v11: No changes.

v10: No changes.

v9: Added Reviewed-by tag. No code changes

v8: Used GENMASK for the mask.

v7: Removed WARN_ON for num_mbm_cntrs. Decided to dynamically allocate the
    bitmap. WARN_ON is not required anymore.
    Removed redundant comments.

v6: Commit message update.
    Renamed abmc_capable to mbm_cntr_assignable.

v5: Name change num_cntrs to num_mbm_cntrs.
    Moved abmc_capable to resctrl_mon.

v4: Removed resctrl_arch_has_abmc(). Added all the code inline. We dont
    need to separate this as arch code.

v3: Removed changes related to mon_features.
    Moved rdt_cpu_has to core.c and added new function resctrl_arch_has_abmc.
    Also moved the fields mbm_assign_capable and mbm_assign_cntrs to
    rdt_resource. (James)

v2: Changed the field name to mbm_assign_capable from abmc_capable.
---
 arch/x86/kernel/cpu/resctrl/monitor.c | 9 +++++++--
 include/linux/resctrl.h               | 4 ++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index aeb2a9283069..fd2761d9f3f7 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -345,6 +345,7 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 	unsigned int mbm_offset = boot_cpu_data.x86_cache_mbm_width_offset;
 	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
 	unsigned int threshold;
+	u32 eax, ebx, ecx, edx;
 
 	snc_nodes_per_l3_cache = snc_get_config();
 
@@ -375,13 +376,17 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
 	resctrl_rmid_realloc_threshold = resctrl_arch_round_mon_val(threshold);
 
 	if (rdt_cpu_has(X86_FEATURE_BMEC)) {
-		u32 eax, ebx, ecx, edx;
-
 		/* Detect list of bandwidth sources that can be tracked */
 		cpuid_count(0x80000020, 3, &eax, &ebx, &ecx, &edx);
 		r->mon.mbm_cfg_mask = ecx & MAX_EVT_CONFIG_BITS;
 	}
 
+	if (rdt_cpu_has(X86_FEATURE_ABMC)) {
+		r->mon.mbm_cntr_assignable = true;
+		cpuid_count(0x80000020, 5, &eax, &ebx, &ecx, &edx);
+		r->mon.num_mbm_cntrs = (ebx & GENMASK(15, 0)) + 1;
+	}
+
 	r->mon_capable = true;
 
 	return 0;
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 2a8fa454d3e6..065fb6e38933 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -260,11 +260,15 @@ enum resctrl_schema_fmt {
  * @num_rmid:		Number of RMIDs available
  * @mbm_cfg_mask:	Bandwidth sources that can be tracked when bandwidth
  *			monitoring events can be configured.
+ * @num_mbm_cntrs:	Number of assignable monitoring counters
+ * @mbm_cntr_assignable:Is system capable of supporting monitor assignment?
  * @evt_list:		List of monitoring events
  */
 struct resctrl_mon {
 	int			num_rmid;
 	unsigned int		mbm_cfg_mask;
+	int			num_mbm_cntrs;
+	bool			mbm_cntr_assignable;
 	struct list_head	evt_list;
 };
 
-- 
2.34.1