[PATCH v2 0/8] x86/resctrl: Support for AMD Global (Slow) Memory Bandwidth Allocation

Babu Moger
2026-04-24T01:41:52Z

This series adds resctrl support for two new AMD memory-bandwidth
allocation features:

- GMBA - Global Memory Bandwidth Allocation (hardware name: GLBE).
Bounds DRAM bandwidth for groups of threads that span
multiple L3 QoS domains, rather than being per-L3 like MBA.

- GSMBA - Global Slow Memory Bandwidth Allocation (hardware name:
GLSBE). The CXL.memory / slow-memory counterpart of GMBA,
analogous to how SMBA relates to MBA.

Both features share a new "NPS-node" control domain: a set of QoS (L3)
domains grouped together and aligned to the system's NPS (Nodes Per
Socket) BIOS configuration. Although the control domain is NPS-scoped,
the underlying bandwidth-limit MSRs (MSR_IA32_GMBA_BW_BASE 0xc0000600,
MSR_IA32_GSMBA_BW_BASE 0xc0000680) are instantiated per L3. Programming
a single control domain therefore requires writing the MSR on one CPU
per L3 that the domain spans - a new pattern for resctrl. Patches 2/8
and 3/8 introduce that infrastructure so the new resources can reuse
it.

The features are documented in:

AMD64 Zen6 Platform Quality of Service (PQOS) Extensions,
Publication # 69193 Revision 1.00, Issue Date March 2026

available at https://bugzilla.kernel.org/show_bug.cgi?id=206537

Series overview
---------------

Patches 1-5 to enable GMBA:

1/8 x86,fs/resctrl: Add support for Global Bandwidth Enforcement (GLBE)

2/8 x86/resctrl: Add RESCTRL_NPS_NODE scope for AMD NPS-aligned domains
Add a new ctrl_scope value for resctrl resources whose control
domain spans multiple L3s within an NPS node.

3/8 x86/resctrl: Update control MSRs per L3 for NPS-scoped resources
Add resctrl_arch_update_nps(): builds a cpumask with one CPU per
distinct L3 in the domain, then issues rdt_ctrl_update() via
smp_call_function_many() on that mask. Falls back to the full
domain mask if the scratch masks cannot be built. Route
resctrl_arch_update_domains() and resctrl_arch_reset_all_ctrls()
through this helper when ctrl_scope == RESCTRL_NPS_NODE.

4/8 x86,fs/resctrl: Add the resource for Global Memory Bandwidth Allocation
Register RDT_RESOURCE_GMBA in rdt_resources_all[] with
ctrl_scope=RESCTRL_NPS_NODE and schema_fmt=RANGE, add commands to
discover feature details.

5/8 fs/resctrl: Add the documentation for Global Memory Bandwidth Allocation
Add examples in Documentation/filesystems/resctrl.rst.

Patches 6-8 to enable GSMBA in the same shape:

6/8 x86,fs/resctrl: Add support for Global Slow Memory Bandwidth Allocation

7/8 x86,fs/resctrl: Add the resource for Global Slow Memory Bandwidth Allocation
Register RDT_RESOURCE_GSMBA with ctrl_scope=RESCTRL_NPS_NODE.

8/8 fs/resctrl: Add the documentation for Global Slow Memory Bandwidth Allocation
Add examples in Documentation/filesystems/resctrl.rst.

Changes since v1
----------------
- Earlier sent RFC(v1) with Global Bandwidth Enforcement (GLBE) and
Privilege Level Zero Association (PLZA). This series only handles
Global Memory Bandwidth Allocation. Both the features are sent separately.

- Documentation
* Fixed grammar in the GMBA / GSMBA sections of resctrl.rst.
* Added examples to update GMBA and GSMBA in resctrl.rst documentation.

- Major changes are releated to RESCTRL_NPS_NODE scope handling.

- Commit messages
* Reworked the changelogs in all the patches.

Previous Revisions:
v1 : https://lore.kernel.org/lkml/cover.1769029977.git.babu.moger@amd.com/
---

base-commit: 216fe4b3e06754e73c79a88b1df7e9806e41f29d

Signed-off-by: Babu Moger <babu.moger@amd.com>

Babu Moger (8):
x86,fs/resctrl: Add support for Global Bandwidth Enforcement (GLBE)
x86/resctrl: Add RESCTRL_NPS_NODE scope for AMD NPS-aligned domains
x86/resctrl: Update control MSRs per L3 for NPS-scoped resources
x86,fs/resctrl: Add the resource for Global Bandwidth Allocation
fs/resctrl: Add the documentation for Global Memory Bandwidth
Allocation
x86,fs/resctrl: Add support for Global Slow Memory Bandwidth
Allocation
x86,fs/resctrl: Add the resource for Global Slow Memory Bandwidth
Allocation
fs/resctrl: Add the documentation for Global Slow Memory Bandwidth
Allocation

.../admin-guide/kernel-parameters.txt | 2 +-
Documentation/filesystems/resctrl.rst | 81 ++++++++++++++
arch/x86/include/asm/cpufeatures.h | 3 +-
arch/x86/include/asm/msr-index.h | 2 +
arch/x86/kernel/cpu/resctrl/core.c | 101 +++++++++++++++++-
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 90 +++++++++++++++-
arch/x86/kernel/cpu/resctrl/internal.h | 1 +
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 15 ++-
arch/x86/kernel/cpu/scattered.c | 2 +
fs/resctrl/ctrlmondata.c | 5 +-
fs/resctrl/rdtgroup.c | 25 ++++-
include/linux/resctrl.h | 3 +
12 files changed, 313 insertions(+), 17 deletions(-)

--
2.43.0