[PATCH v12 12/26] x86/resctrl: Add data structures and definitions for ABMC assignment

Babu Moger
2025-04-04T00:20:39Z

The ABMC feature provides an option to the user to assign a hardware
counter to an RMID, event pair and monitor the bandwidth as long as the
counter is assigned. The bandwidth events will be tracked by the hardware
until the user changes the configuration. Each resctrl group can configure
maximum two counters, one for total event and one for local event.

The ABMC feature implements an MSR L3_QOS_ABMC_CFG (C000_03FDh).
Configuration is done by setting the counter id, bandwidth source (RMID)
and bandwidth configuration supported by BMEC (Bandwidth Monitoring Event
Configuration).

Attempts to read or write the MSR when ABMC is not enabled will result
in a #GP(0) exception.

Introduce the data structures and definitions for MSR L3_QOS_ABMC_CFG
(0xC000_03FDh):
=========================================================================
Bits Mnemonic Description Access Reset
Type Value
=========================================================================
63 CfgEn Configuration Enable R/W 0

62 CtrEn Enable/disable counting R/W 0

61:53 – Reserved MBZ 0

52:48 CtrID Counter Identifier R/W 0

47 IsCOS BwSrc field is a CLOSID R/W 0
(not an RMID)

46:44 – Reserved MBZ 0

43:32 BwSrc Bandwidth Source R/W 0
(RMID or CLOSID)

31:0 BwType Bandwidth configuration R/W 0
to track for this counter
==========================================================================

The feature details are documented in the 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).

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Signed-off-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
---
v12: No changes.

v11: No changes.

v10: No changes.

v9: Removed the references of L3_QOS_ABMC_DSC.
Text changes about configuration in kernel doc.

v8: Update the configuration notes in kernel_doc.
Few commit message update.

v7: Removed the reference of L3_QOS_ABMC_DSC as it is not used anymore.
Moved the configuration notes to kernel_doc.
Adjusted the tabs for l3_qos_abmc_cfg and checkpatch seems happy.

v6: Removed all the fs related changes.
Added note on CfgEn,CtrEn.
Removed the definitions which are not used.
Removed cntr_id initialization.

v5: Moved assignment flags here (path 10/19 of v4).
Added MON_CNTR_UNSET definition to initialize cntr_id's.
More details in commit log.
Renamed few fields in l3_qos_abmc_cfg for readability.

v4: Added more descriptions.
Changed the name abmc_ctr_id to ctr_id.
Added L3_QOS_ABMC_DSC. Used for reading the configuration.

v3: No changes.

v2: No changes.
---
arch/x86/include/asm/msr-index.h | 1 +
arch/x86/kernel/cpu/resctrl/internal.h | 35 ++++++++++++++++++++++++++
2 files changed, 36 insertions(+)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index cb3c0720d910..17f80eec2202 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -1201,6 +1201,7 @@
/* - AMD: */
#define MSR_IA32_MBA_BW_BASE 0xc0000200
#define MSR_IA32_SMBA_BW_BASE 0xc0000280
+#define MSR_IA32_L3_QOS_ABMC_CFG 0xc00003fd
#define MSR_IA32_L3_QOS_EXT_CFG 0xc00003ff
#define MSR_IA32_EVT_CFG_BASE 0xc0000400

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index e4b169fd6970..0b73ec451d2c 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -483,6 +483,41 @@ union cpuid_0x10_x_edx {
unsigned int full;
};

+/*
+ * ABMC counters are configured by writing to L3_QOS_ABMC_CFG.
+ * @bw_type : Bandwidth configuration (supported by BMEC)
+ * tracked by the @cntr_id.
+ * @bw_src : Bandwidth source (RMID or CLOSID).
+ * @reserved1 : Reserved.
+ * @is_clos : @bw_src field is a CLOSID (not an RMID).
+ * @cntr_id : Counter identifier.
+ * @reserved : Reserved.
+ * @cntr_en : Counting enable bit.
+ * @cfg_en : Configuration enable bit.
+ *
+ * Configuration and counting:
+ * Counter can be configured across multiple writes to MSR. Configuration
+ * is applied only when @cfg_en = 1. Counter @cntr_id is reset when the
+ * configuration is applied.
+ * @cfg_en = 1, @cntr_en = 0 : Apply @cntr_id configuration but do not
+ * count events.
+ * @cfg_en = 1, @cntr_en = 1 : Apply @cntr_id configuration and start
+ * counting events.
+ */
+union l3_qos_abmc_cfg {
+ struct {
+ unsigned long bw_type :32,
+ bw_src :12,
+ reserved1: 3,
+ is_clos : 1,
+ cntr_id : 5,
+ reserved : 9,
+ cntr_en : 1,
+ cfg_en : 1;
+ } split;
+ unsigned long full;
+};
+
void rdt_last_cmd_clear(void);
void rdt_last_cmd_puts(const char *s);
__printf(1, 2)
--
2.34.1