linux.git/arch/riscv/kernel/qos.c, branch master Linux kernel source tree riscv: Add support for srmcfg CSR from Ssqosid extension 2026-08-08T01:24:32+00:00 Drew Fustini fustini@kernel.org 2026-08-08T01:24:32+00:00 326ba66db9494e71ddcafd1c4c063b49c3101495 Add support for the srmcfg CSR defined in the Ssqosid ISA extension. The CSR contains two fields: - Resource Control ID (RCID) for resource allocation - Monitoring Counter ID (MCID) for tracking resource usage Requests from a hart to shared resources are tagged with these IDs, allowing resource usage to be associated with the running task. Add a srmcfg field to thread_struct with the same format as the CSR. The context-switch path writes the field to the CSR, and resctrl_arch_set_closid_rmid() updates it when a task is assigned to a resctrl control or monitoring group. A per-cpu cpu_srmcfg_default holds the default srmcfg for each CPU, set by resctrl_arch_set_cpu_default_closid_rmid() on CPU group assignment. On context switch, RCID and MCID inherit from the CPU default independently: a task whose thread RCID field is zero takes the CPU default's RCID, and likewise for MCID. A per-cpu cpu_srmcfg variable mirrors the CSR state to avoid redundant writes. L1D-hot memory access is faster than a CSR read and avoids traps under virtualization. Link: https://github.com/riscv/riscv-ssqosid/releases/tag/v1.0 Assisted-by: Claude:claude-opus-4-7 Co-developed-by: Kornel Dulęba <mindal@semihalf.com> Signed-off-by: Kornel Dulęba <mindal@semihalf.com> Signed-off-by: Drew Fustini <fustini@kernel.org> Link: https://patch.msgid.link/20260729-dfustini-atl-sc-cbqri-dt-v6-3-7c22b05d461b@kernel.org Signed-off-by: Paul Walmsley <pjw@kernel.org> 
Add support for the srmcfg CSR defined in the Ssqosid ISA extension.
The CSR contains two fields:

  - Resource Control ID (RCID) for resource allocation
  - Monitoring Counter ID (MCID) for tracking resource usage

Requests from a hart to shared resources are tagged with these IDs,
allowing resource usage to be associated with the running task.

Add a srmcfg field to thread_struct with the same format as the CSR.
The context-switch path writes the field to the CSR, and
resctrl_arch_set_closid_rmid() updates it when a task is assigned to a
resctrl control or monitoring group.

A per-cpu cpu_srmcfg_default holds the default srmcfg for each CPU, set
by resctrl_arch_set_cpu_default_closid_rmid() on CPU group assignment.
On context switch, RCID and MCID inherit from the CPU default
independently: a task whose thread RCID field is zero takes the CPU
default's RCID, and likewise for MCID.

A per-cpu cpu_srmcfg variable mirrors the CSR state to avoid
redundant writes. L1D-hot memory access is faster than a CSR read and
avoids traps under virtualization.

Link: https://github.com/riscv/riscv-ssqosid/releases/tag/v1.0
Assisted-by: Claude:claude-opus-4-7
Co-developed-by: Kornel Dulęba <mindal@semihalf.com>
Signed-off-by: Kornel Dulęba <mindal@semihalf.com>
Signed-off-by: Drew Fustini <fustini@kernel.org>
Link: https://patch.msgid.link/20260729-dfustini-atl-sc-cbqri-dt-v6-3-7c22b05d461b@kernel.org
Signed-off-by: Paul Walmsley <pjw@kernel.org>