diff --git a/arch/csr/Ssqosid/srmcfg.yaml b/arch/csr/Ssqosid/srmcfg.yaml
new file mode 100644
index 000000000..74c86e85a
--- /dev/null
+++ b/arch/csr/Ssqosid/srmcfg.yaml
@@ -0,0 +1,152 @@
+# yaml-language-server: $schema=../../../schemas/csr_schema.json
+$schema: csr_schema.json#
+kind: csr
+name: srmcfg
+long_name: Supervisor Resource Management Configuration
+address: 0x181
+priv_mode: S
+length: SXLEN
+definedBy: Ssqosid
+description:
+  - id: csr-srmcfg-purpose
+    normative: true
+    text: |
+      The `srmcfg` register is used to configure a Resource Control ID (`RCID`) and a Monitoring Counter ID (`MCID`).
+      Both `RCID` and `MCID` are WARL fields.
+
+  - id: csr-`srmcfg`-field-usage
+    normative: true
+    text: |
+      The `RCID` and `MCID` accompany each request made by the hart to shared resource controllers.
+      The `RCID` is used to determine the resource allocations (e.g., cache occupancy limits, memory bandwidth limits, etc.) to enforce.
+      The `MCID` is used to identify a counter to monitor resource usage.
+
+  - id: csr-srmcfg-default-scope
+    normative: true
+    text: |
+      The `RCID` and `MCID` configured in the `srmcfg` CSR apply to all privilege modes of software execution on that hart by default,
+      but this behavior may be overridden by future extensions.
+
+  - id: csr-srmcfg-smstateen-interaction
+    normative: true
+    text: |
+      If extension `Smstateen` is implemented together with `Ssqosid`, then `Ssqosid` also requires the `SRMCFG` bit in `mstateen0` to be implemented.
+      If `mstateen0.SRMCFG` is `0`, attempts to access `srmcfg` in privilege modes less privileged than M-mode raise an illegal-instruction exception.
+
+  - id: csr-srmcfg-vsmode-exception
+    normative: true
+    text: |
+      If `mstateen0.SRMCFG` is `1` or if extension `Smstateen` is not implemented, attempts to access `srmcfg` when `V=1` raise a virtual-instruction exception.
+
+  - id: csr-srmcfg-rcid-reset
+    normative: false
+    text: |
+      A reset value of `0` is suggested for the `RCID` field, matching resource controllers' default behavior of associating all capacity with `RCID=0`.
+
+  - id: csr-srmcfg-mcid-reset
+    normative: false
+    text: |
+      The `MCID` reset value does not affect functionality and may be implementation-defined.
+
+  - id: csr-srmcfg-id-bit-allocation
+    normative: false
+    text: |
+      Typically, fewer bits are allocated for `RCID` (e.g., to support tens of `RCID`s) than for `MCID` (e.g., to support hundreds of `MCID`s).
+
+  - id: csr-srmcfg-rcid-grouping
+    normative: false
+    text: |
+      A common `RCID` is usually used to group apps or VMs, pooling resource allocations to meet collective SLAs.
+
+  - id: csr-srmcfg-mcid-granularity
+    normative: false
+    text: |
+      If an SLA breach occurs, unique `MCID`s enable granular monitoring, aiding decisions on resource adjustment,
+      associating a different `RCID` with a subset of members, or migrating members to other machines.
+      The larger pool of `MCID`s speeds up this analysis.
+
+  - id: csr-srmcfg-privilege-behavior
+    normative: false
+    text: |
+      The `RCID` and `MCID` in `srmcfg` apply across all privilege levels on the hart.
+      Typically, higher-privilege modes don't modify `srmcfg`, as they often serve lower-privileged tasks.
+      If differentiation is needed, higher privilege code can update `srmcfg` and restore it before returning to a lower privilege level.
+
+  - id: csr-srmcfg-vm-virtualization
+    normative: false
+    text: |
+      In VM environments, hypervisors usually manage resource allocations, keeping the Guest OS out of QoS flows.
+      If needed, the hypervisor can virtualize the `srmcfg` CSR for a VM using the virtual-instruction exceptions triggered upon Guest access.
+
+  - id: csr-srmcfg-vs-mode-future
+    normative: false
+    text: |
+      If the direct selection of `RCID` and `MCID` by the VM becomes common and emulation overhead is an issue,
+      future extensions may allow VS-mode to use a selector for a hypervisor-configured set of CSRs holding `RCID` and `MCID` values designated for that Guest OS use.
+
+  - id: csr-srmcfg-context-switch
+    normative: false
+    text: |
+      During context switches, the supervisor may choose to execute with the `srmcfg` of the outgoing context to attribute the execution to it.
+      Prior to restoring the new context, it switches to the new VM’s `srmcfg`.
+      The supervisor can also use a separate configuration for execution not to be attributed to either context.
+fields:
+  RCID:
+    location: 11-0
+    type: RW
+    long_name: Resource Control ID
+    description: |
+      The `RCID` is used to determine the resource allocations (e.g., cache occupancy limits,
+      memory bandwidth limits, etc.) to enforce.
+    reset_value: UNDEFINED_LEGAL
+    sw_write(csr_value): |
+      if (implemented?(ExtensionName::Smstateen)) {
+        if (mode() < PrivilegeMode::M && CSR[mstateen0].SRMCFG == 0) {
+          raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
+        }
+        if (virtual_mode?() && CSR[mstateen0].SRMCFG == 1) {
+          raise(ExceptionCode::VirtualInstruction, mode(), $encoding);
+        }
+      } else {
+        if (virtual_mode?()) {
+          raise(ExceptionCode::VirtualInstruction, mode(), $encoding);
+        }
+      }
+      return csr_value.RCID & ((1 `<< RCID_WIDTH) - 1);
+
+  MCID:
+    location: 27-16
+    type: RW
+    long_name: Monitoring Counter ID
+    description: |
+      The `MCID` is used to identify a counter to monitor resource usage.
+    reset_value: UNDEFINED_LEGAL
+    sw_write(csr_value): |
+      if (implemented?(ExtensionName::Smstateen)) {
+        if (mode() < PrivilegeMode::M && CSR[mstateen0].SRMCFG == 0) {
+          raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
+        }
+        if (virtual_mode?() && CSR[mstateen0].SRMCFG == 1) {
+          raise(ExceptionCode::VirtualInstruction, mode(), $encoding);
+        }
+      } else {
+        if (virtual_mode?()) {
+          raise(ExceptionCode::VirtualInstruction, mode(), $encoding);
+        }
+      }
+      return csr_value.MCID & ((1 `<< MCID_WIDTH) - 1);
+
+sw_read(): |
+  if (implemented?(ExtensionName::Smstateen)) {
+    if (mode() < PrivilegeMode::M && CSR[mstateen0].SRMCFG == 0) {
+      raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
+    }
+    if (virtual_mode?() && CSR[mstateen0].SRMCFG == 1) {
+      raise(ExceptionCode::VirtualInstruction, mode(), $encoding);
+    }
+  } else {
+    if (virtual_mode?()) {
+      raise(ExceptionCode::VirtualInstruction, mode(), $encoding);
+    }
+  }
+  return $bits(CSR[mstateen0]);
diff --git a/arch/csr/mstateen0.yaml b/arch/csr/mstateen0.yaml
index 314f9ace2..309884256 100644
--- a/arch/csr/mstateen0.yaml
+++ b/arch/csr/mstateen0.yaml
@@ -129,7 +129,7 @@ fields:
   SRMCFG:
     long_name: srmcfg access control
     location: 55
-    #definedBy: Ssqosid
+    definedBy: Ssqosid
     description: |
       The SRMCFG bit in `mstateen0` controls access to the `srmcfg`` CSR introduced by the Ssqosid Chapter 18
       extension.
diff --git a/arch/csr/mstateen0h.yaml b/arch/csr/mstateen0h.yaml
index 036910f19..39fdfa80f 100644
--- a/arch/csr/mstateen0h.yaml
+++ b/arch/csr/mstateen0h.yaml
@@ -111,7 +111,7 @@ fields:
   SRMCFG:
     long_name: srmcfg access control
     location: 23
-    #definedBy: Ssqosid
+    definedBy: Ssqosid
     alias: mstateen0.SRMCFG
     sw_write(csr_value): |
       CSR[mstateen0].SRMCFG = csr_value.SRMCFG;
diff --git a/arch/ext/Ssqosid.yaml b/arch/ext/Ssqosid.yaml
new file mode 100644
index 000000000..49225dffb
--- /dev/null
+++ b/arch/ext/Ssqosid.yaml
@@ -0,0 +1,55 @@
+# yaml-language-server: $schema=../../schemas/ext_schema.json
+
+$schema: "ext_schema.json#"
+kind: extension
+name: Ssqosid
+type: privileged
+long_name: Quality-of-Service Identifiers
+description: |
+  Quality of Service (QoS) is defined as the minimal end-to-end performance guaranteed in advance by a service level agreement (SLA) to a workload.
+  Performance metrics might include measures such as instructions per cycle (IPC), latency of service, etc.
+
+  When multiple workloads execute concurrently on modern processors—equipped with large core counts, multiple cache hierarchies, and multiple memory
+  controllers—the performance of any given workload becomes less deterministic, or even non-deterministic, due to shared resource contention.
+
+  To manage performance variability, system software needs resource allocation and monitoring capabilities.
+  These capabilities allow for the reservation of resources like cache and bandwidth, thus meeting individual performance targets while minimizing interference.
+  For resource management, hardware should provide monitoring features that allow system software to profile workload resource consumption and allocate resources accordingly.
+
+  To facilitate this, the QoS Identifiers extension (Ssqosid) introduces the srmcfg register,
+  which configures a hart with two identifiers: a Resource Control ID (RCID) and a Monitoring Counter ID (MCID).
+  These identifiers accompany each request issued by the hart to shared resource controllers.
+
+  Additional metadata, like the nature of the memory access and the ID of the originating supervisor domain,
+  can accompany RCID and MCID. Resource controllers may use this metadata for differentiated service such as a different capacity allocation for code storage vs. data storage.
+  Resource controllers can use this data for security policies such as not exposing statistics of one security domain to another.
+
+  These identifiers are crucial for the RISC-V Capacity and Bandwidth Controller QoS Register Interface (CBQRI) specification,
+  which provides methods for setting resource usage limits and monitoring resource consumption.
+  The RCID controls resource allocations, while the MCID is used for tracking resource usage.
+
+params:
+  RCID_WIDTH:
+    description: |
+      Number of bits used for the Resource Control ID field (RCID).
+      Default is 12.
+    schema:
+      type: integer
+      minimum: 1
+      maximum: 12
+
+  MCID_WIDTH:
+    description: |
+      Number of bits used for the Monitoring Counter ID field (MCID).
+      Default is 12.
+    schema:
+      type: integer
+      minimum: 1
+      maximum: 12
+
+versions:
+  - version: "1.0.0"
+    state: ratified
+    ratification_date: "2024-06"
+    url: "https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-isa-release-5308687-2025-04-22"
+    requires: { name: S, version: ~> 1.13 }