[PATCH v4 05/13] x86/cpufeatures: Add Bandwidth Monitoring Event Configuration feature flag

Babu Moger
2022-09-07T18:01:08Z

Newer AMD processors support the new feature Bandwidth Monitoring Event
Configuration (BMEC).

Support of this feature is available via CPUID Fn8000_0020_EBX_x0 (ECX=0).
Bits Field Name Description
3 EVT_CFG Bandwidth Monitoring Event Configuration (BMEC)

Currently, the bandwidth monitoring events mbm_total_bytes and
mbm_local_bytes are set to count all the total and local reads/writes
respectively. With the introduction of SLOW memory, the two counters are
not enough to count all the different types of memory events. With the
feature BMEC, the users have the option to configure mbm_total_bytes and
mbm_local_bytes to count the specific type of events.

Each BMEC event has a configuration MSR, QOS_EVT_CFG (0x000_0400h +
EventID) which contains one field for each Bandwidth Type that can be used
to configure the bandwidth event to track any combination of supported
bandwidth types. The event will count requests from every Bandwidth Type
bit that is set in the corresponding configuration register.

Following are the types of events supported:

==== ========================================================
Bits Description
==== ========================================================
6 Dirty Victims from the QOS domain to all types of memory
5 Reads to slow memory in the non-local NUMA domain
4 Reads to slow memory in the local NUMA domain
3 Non-temporal writes to non-local NUMA domain
2 Non-temporal writes to local NUMA domain
1 Reads to memory in the non-local NUMA domain
0 Reads to memory in the local NUMA domain
==== ========================================================

By default, the mbm_total_bytes configuration is set to 0x7F to count
all the event types and the mbm_local_bytes configuration is set to
0x15 to count all the local memory events.

Feature description is available in the specification, "AMD64 Technology
Platform Quality of Service Extensions, Revision: 1.03 Publication # 56375
Revision: 1.03 Issue Date: February 2022".

Link: https://www.amd.com/en/support/tech-docs/amd64-technology-platform-quality-service-extensions
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Signed-off-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/kernel/cpu/scattered.c | 1 +
2 files changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 1815435c9c88..a4ee02a56d54 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -305,6 +305,7 @@
#define X86_FEATURE_USE_IBPB_FW (11*32+16) /* "" Use IBPB during runtime firmware calls */
#define X86_FEATURE_RSB_VMEXIT_LITE (11*32+17) /* "" Fill RSB on VM exit when EIBRS is enabled */
#define X86_FEATURE_SMBA (11*32+18) /* SLOW Memory Bandwidth Allocation */
+#define X86_FEATURE_BMEC (11*32+18) /* AMD Bandwidth Monitoring Event Configuration (BMEC) */

/* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
#define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index 885ecf46abb2..7981df0b910e 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -45,6 +45,7 @@ static const struct cpuid_bit cpuid_bits[] = {
{ X86_FEATURE_PROC_FEEDBACK, CPUID_EDX, 11, 0x80000007, 0 },
{ X86_FEATURE_MBA, CPUID_EBX, 6, 0x80000008, 0 },
{ X86_FEATURE_SMBA, CPUID_EBX, 2, 0x80000020, 0 },
+ { X86_FEATURE_BMEC, CPUID_EBX, 3, 0x80000020, 0 },
{ X86_FEATURE_PERFMON_V2, CPUID_EAX, 0, 0x80000022, 0 },
{ 0, 0, 0, 0, 0 }
};