sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

5 files changed, 701 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/edac/altr,socfpga-ecc-manager.yaml b/Documentation/devicetree/bindings/edac/altr,socfpga-ecc-manager.yaml
new file mode 100644
index 000000000..136e8fccd
--- /dev/null
+++ b/Documentation/devicetree/bindings/edac/altr,socfpga-ecc-manager.yaml
@@ -0,0 +1,324 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright (C) 2025 Altera Corporation
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/edac/altr,socfpga-ecc-manager.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Altera SoCFPGA ECC Manager
+
+maintainers:
+  - Niravkumar L Rabara <niravkumarlaxmidas.rabara@altera.com>
+
+description:
+  This binding describes the device tree nodes required for the Altera SoCFPGA
+  ECC Manager for the Cyclone5, Arria5, Arria10, Stratix10, and Agilex chip
+  families.
+
+properties:
+
+  compatible:
+    oneOf:
+      - items:
+          - const: altr,socfpga-s10-ecc-manager
+          - const: altr,socfpga-a10-ecc-manager
+      - const: altr,socfpga-a10-ecc-manager
+      - const: altr,socfpga-ecc-manager
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 1
+
+  interrupts:
+    minItems: 1
+    maxItems: 2
+
+  interrupt-controller: true
+
+  "#interrupt-cells":
+    const: 2
+
+  ranges: true
+
+  altr,sysmgr-syscon:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description: phandle to Stratix10 System Manager Block with the ECC manager registers
+
+  sdramedac:
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        enum:
+          - altr,sdram-edac
+          - altr,sdram-edac-a10
+          - altr,sdram-edac-s10
+
+      interrupts:
+        minItems: 1
+        maxItems: 2
+
+      altr,sdr-syscon:
+        $ref: /schemas/types.yaml#/definitions/phandle
+        description: phandle to SDRAM parent
+
+    required:
+      - compatible
+      - interrupts
+      - altr,sdr-syscon
+
+patternProperties:
+  "^ocram-ecc@[a-f0-9]+$":
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        oneOf:
+          - items:
+              - const: altr,socfpga-s10-ocram-ecc
+              - const: altr,socfpga-a10-ocram-ecc
+          - const: altr,socfpga-a10-ocram-ecc
+          - const: altr,socfpga-ocram-ecc
+
+      reg:
+        maxItems: 1
+
+      interrupts:
+        minItems: 1
+        maxItems: 2
+
+      iram:
+        $ref: /schemas/types.yaml#/definitions/phandle
+        description: phandle to OCRAM parent
+
+      altr,ecc-parent:
+        $ref: /schemas/types.yaml#/definitions/phandle
+        description: phandle to OCRAM parent
+
+    required:
+      - compatible
+      - reg
+      - interrupts
+
+  "^usb[0-9]-ecc@[a-f0-9]+$":
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        oneOf:
+          - items:
+              - const: altr,socfpga-s10-usb-ecc
+              - const: altr,socfpga-usb-ecc
+          - const: altr,socfpga-usb-ecc
+
+      reg:
+        maxItems: 1
+
+      interrupts:
+        minItems: 1
+        maxItems: 2
+
+      altr,ecc-parent:
+        $ref: /schemas/types.yaml#/definitions/phandle
+        description: phandle to USB parent
+
+    required:
+      - compatible
+      - reg
+      - interrupts
+      - altr,ecc-parent
+
+  "^emac[0-9]-[t,r]x-ecc@[a-f0-9]+$":
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        oneOf:
+          - items:
+              - const: altr,socfpga-s10-eth-mac-ecc
+              - const: altr,socfpga-eth-mac-ecc
+          - const: altr,socfpga-eth-mac-ecc
+
+      reg:
+        maxItems: 1
+
+      interrupts:
+        minItems: 1
+        maxItems: 2
+
+      altr,ecc-parent:
+        $ref: /schemas/types.yaml#/definitions/phandle
+        description: phandle to ethernet parent
+
+    required:
+      - compatible
+      - reg
+      - interrupts
+      - altr,ecc-parent
+
+  "^sdmmc[a-f]-ecc@[a-f0-9]+$":
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        oneOf:
+          - items:
+              - const: altr,socfpga-s10-sdmmc-ecc
+              - const: altr,socfpga-sdmmc-ecc
+          - const: altr,socfpga-sdmmc-ecc
+
+      reg:
+        maxItems: 1
+
+      interrupts:
+        minItems: 2
+        maxItems: 4
+
+      altr,ecc-parent:
+        $ref: /schemas/types.yaml#/definitions/phandle
+        description: phandle to SD/MMC parent
+
+    required:
+      - compatible
+      - reg
+      - interrupts
+      - altr,ecc-parent
+
+  "^l2-ecc@[a-f0-9]+$":
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        enum:
+          - altr,socfpga-a10-l2-ecc
+          - altr,socfpga-l2-ecc
+
+      reg:
+        maxItems: 1
+
+      interrupts:
+        maxItems: 2
+
+    required:
+      - compatible
+      - reg
+      - interrupts
+
+  "^dma-ecc@[a-f0-9]+$":
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        const: altr,socfpga-dma-ecc
+      reg:
+        maxItems: 1
+
+      interrupts:
+        maxItems: 2
+
+      altr,ecc-parent:
+        $ref: /schemas/types.yaml#/definitions/phandle
+        description: phandle to SD/MMC parent
+
+    required:
+      - compatible
+      - reg
+      - interrupts
+      - altr,ecc-parent
+
+if:
+  properties:
+    compatible:
+      contains:
+        const: altr,socfpga-ecc-manager
+then:
+  required:
+    - compatible
+    - "#address-cells"
+    - "#size-cells"
+    - ranges
+
+else:
+  required:
+    - compatible
+    - "#address-cells"
+    - "#size-cells"
+    - interrupts
+    - interrupt-controller
+    - "#interrupt-cells"
+    - ranges
+    - altr,sysmgr-syscon
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+    eccmgr {
+        compatible = "altr,socfpga-s10-ecc-manager",
+                     "altr,socfpga-a10-ecc-manager";
+        altr,sysmgr-syscon = <&sysmgr>;
+        #address-cells = <1>;
+        #size-cells = <1>;
+        interrupts = <GIC_SPI 15 IRQ_TYPE_LEVEL_HIGH>;
+        interrupt-controller;
+        #interrupt-cells = <2>;
+        ranges;
+
+        sdramedac {
+            compatible = "altr,sdram-edac-s10";
+            altr,sdr-syscon = <&sdr>;
+            interrupts = <16 IRQ_TYPE_LEVEL_HIGH>;
+        };
+
+        ocram-ecc@ff8cc000 {
+            compatible = "altr,socfpga-s10-ocram-ecc",
+                         "altr,socfpga-a10-ocram-ecc";
+            reg = <0xff8cc000 0x100>;
+            altr,ecc-parent = <&ocram>;
+            interrupts = <1 IRQ_TYPE_LEVEL_HIGH>;
+        };
+
+        usb0-ecc@ff8c4000 {
+            compatible = "altr,socfpga-s10-usb-ecc",
+                         "altr,socfpga-usb-ecc";
+            reg = <0xff8c4000 0x100>;
+            altr,ecc-parent = <&usb0>;
+            interrupts = <2 IRQ_TYPE_LEVEL_HIGH>;
+        };
+
+        emac0-rx-ecc@ff8c0000 {
+            compatible = "altr,socfpga-s10-eth-mac-ecc",
+                         "altr,socfpga-eth-mac-ecc";
+            reg = <0xff8c0000 0x100>;
+            altr,ecc-parent = <&gmac0>;
+            interrupts = <4 IRQ_TYPE_LEVEL_HIGH>;
+        };
+
+        emac0-tx-ecc@ff8c0400 {
+            compatible = "altr,socfpga-s10-eth-mac-ecc",
+                         "altr,socfpga-eth-mac-ecc";
+            reg = <0xff8c0400 0x100>;
+            altr,ecc-parent = <&gmac0>;
+            interrupts = <5 IRQ_TYPE_LEVEL_HIGH>;
+        };
+
+        sdmmca-ecc@ff8c8c00 {
+            compatible = "altr,socfpga-s10-sdmmc-ecc",
+                         "altr,socfpga-sdmmc-ecc";
+            reg = <0xff8c8c00 0x100>;
+            altr,ecc-parent = <&mmc>;
+            interrupts = <14 IRQ_TYPE_LEVEL_HIGH>,
+                         <15 IRQ_TYPE_LEVEL_HIGH>;
+        };
+    };
diff --git a/Documentation/devicetree/bindings/edac/amazon,al-mc-edac.yaml b/Documentation/devicetree/bindings/edac/amazon,al-mc-edac.yaml
new file mode 100644
index 000000000..4cfc3a187
--- /dev/null
+++ b/Documentation/devicetree/bindings/edac/amazon,al-mc-edac.yaml
@@ -0,0 +1,66 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/edac/amazon,al-mc-edac.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Amazon's Annapurna Labs Memory Controller EDAC
+
+maintainers:
+  - Talel Shenhar <talel@amazon.com>
+  - Talel Shenhar <talelshenhar@gmail.com>
+
+description: |
+  EDAC node is defined to describe on-chip error detection and correction for
+  Amazon's Annapurna Labs Memory Controller.
+
+properties:
+
+  compatible:
+    const: amazon,al-mc-edac
+
+  reg:
+    maxItems: 1
+
+  "#address-cells":
+    const: 2
+
+  "#size-cells":
+    const: 2
+
+  interrupts:
+    minItems: 1
+    items:
+      - description: uncorrectable error interrupt
+      - description: correctable error interrupt
+
+  interrupt-names:
+    minItems: 1
+    items:
+      - const: ue
+      - const: ce
+
+required:
+  - compatible
+  - reg
+  - "#address-cells"
+  - "#size-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    soc {
+        #address-cells = <2>;
+        #size-cells = <2>;
+        edac@f0080000 {
+          #address-cells = <2>;
+          #size-cells = <2>;
+          compatible = "amazon,al-mc-edac";
+          reg = <0x0 0xf0080000 0x0 0x00010000>;
+          interrupt-parent = <&amazon_al_system_fabric>;
+          interrupt-names = "ue";
+          interrupts = <20 IRQ_TYPE_LEVEL_HIGH>;
+        };
+    };
diff --git a/Documentation/devicetree/bindings/edac/apm,xgene-edac.yaml b/Documentation/devicetree/bindings/edac/apm,xgene-edac.yaml
new file mode 100644
index 000000000..9637df7af
--- /dev/null
+++ b/Documentation/devicetree/bindings/edac/apm,xgene-edac.yaml
@@ -0,0 +1,202 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/edac/apm,xgene-edac.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: APM X-Gene SoC EDAC
+
+maintainers:
+  - Khuong Dinh <khuong@os.amperecomputing.com>
+
+description: >
+  EDAC node is defined to describe on-chip error detection and correction.
+
+  The following error types are supported:
+
+    memory controller  - Memory controller
+    PMD (L1/L2)        - Processor module unit (PMD) L1/L2 cache
+    L3                 - L3 cache controller
+    SoC                - SoC IPs such as Ethernet, SATA, etc
+
+properties:
+  compatible:
+    const: apm,xgene-edac
+
+  reg:
+    items:
+      - description: CPU bus (PCP) resource
+
+  '#address-cells':
+    const: 2
+
+  '#size-cells':
+    const: 2
+
+  ranges: true
+
+  interrupts:
+    description: Interrupt-specifier for MCU, PMD, L3, or SoC error IRQ(s).
+    items:
+      - description: MCU error IRQ
+      - description: PMD error IRQ
+      - description: L3 error IRQ
+      - description: SoC error IRQ
+    minItems: 1
+
+  regmap-csw:
+    description: Regmap of the CPU switch fabric (CSW) resource.
+    $ref: /schemas/types.yaml#/definitions/phandle
+
+  regmap-mcba:
+    description: Regmap of the MCB-A (memory bridge) resource.
+    $ref: /schemas/types.yaml#/definitions/phandle
+
+  regmap-mcbb:
+    description: Regmap of the MCB-B (memory bridge) resource.
+    $ref: /schemas/types.yaml#/definitions/phandle
+
+  regmap-efuse:
+    description: Regmap of the PMD efuse resource.
+    $ref: /schemas/types.yaml#/definitions/phandle
+
+  regmap-rb:
+    description: Regmap of the register bus resource (optional for compatibility).
+    $ref: /schemas/types.yaml#/definitions/phandle
+
+required:
+  - compatible
+  - regmap-csw
+  - regmap-mcba
+  - regmap-mcbb
+  - regmap-efuse
+  - reg
+  - interrupts
+
+# Child-node bindings
+patternProperties:
+  '^edacmc@':
+    description: Memory controller subnode
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        const: apm,xgene-edac-mc
+
+      reg:
+        maxItems: 1
+
+      memory-controller:
+        description: Instance number of the memory controller.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        maximum: 3
+
+    required:
+      - compatible
+      - reg
+      - memory-controller
+
+  '^edacpmd@':
+    description: PMD subnode
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        const: apm,xgene-edac-pmd
+
+      reg:
+        maxItems: 1
+
+      pmd-controller:
+        description: Instance number of the PMD controller.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        maximum: 3
+
+    required:
+      - compatible
+      - reg
+      - pmd-controller
+
+  '^edacl3@':
+    description: L3 subnode
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        enum:
+          - apm,xgene-edac-l3
+          - apm,xgene-edac-l3-v2
+
+      reg:
+        maxItems: 1
+
+    required:
+      - compatible
+      - reg
+
+  '^edacsoc@':
+    description: SoC subnode
+    type: object
+    additionalProperties: false
+
+    properties:
+      compatible:
+        enum:
+          - apm,xgene-edac-soc
+          - apm,xgene-edac-soc-v1
+
+      reg:
+        maxItems: 1
+
+    required:
+      - compatible
+      - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    bus {
+        #address-cells = <2>;
+        #size-cells = <2>;
+
+        edac@78800000 {
+            compatible = "apm,xgene-edac";
+            reg = <0x0 0x78800000 0x0 0x100>;
+            #address-cells = <2>;
+            #size-cells = <2>;
+            ranges;
+            interrupts = <0x0 0x20 0x4>, <0x0 0x21 0x4>, <0x0 0x27 0x4>;
+
+            regmap-csw = <&csw>;
+            regmap-mcba = <&mcba>;
+            regmap-mcbb = <&mcbb>;
+            regmap-efuse = <&efuse>;
+            regmap-rb = <&rb>;
+
+            edacmc@7e800000 {
+                compatible = "apm,xgene-edac-mc";
+                reg = <0x0 0x7e800000 0x0 0x1000>;
+                memory-controller = <0>;
+            };
+
+            edacpmd@7c000000 {
+                compatible = "apm,xgene-edac-pmd";
+                reg = <0x0 0x7c000000 0x0 0x200000>;
+                pmd-controller = <0>;
+            };
+
+            edacl3@7e600000 {
+                compatible = "apm,xgene-edac-l3";
+                reg = <0x0 0x7e600000 0x0 0x1000>;
+            };
+
+            edacsoc@7e930000 {
+                compatible = "apm,xgene-edac-soc-v1";
+                reg = <0x0 0x7e930000 0x0 0x1000>;
+            };
+        };
+    };
diff --git a/Documentation/devicetree/bindings/edac/aspeed,ast2400-sdram-edac.yaml b/Documentation/devicetree/bindings/edac/aspeed,ast2400-sdram-edac.yaml
new file mode 100644
index 000000000..09735826d
--- /dev/null
+++ b/Documentation/devicetree/bindings/edac/aspeed,ast2400-sdram-edac.yaml
@@ -0,0 +1,48 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/edac/aspeed,ast2400-sdram-edac.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Aspeed BMC SoC SDRAM EDAC controller
+
+maintainers:
+  - Stefan Schaeckeler <sschaeck@cisco.com>
+
+description: >
+  The Aspeed BMC SoC supports DDR3 and DDR4 memory with and without ECC (error
+  correction check).
+
+  The memory controller supports SECDED (single bit error correction, double bit
+  error detection) and single bit error auto scrubbing by reserving 8 bits for
+  every 64 bit word (effectively reducing available memory to 8/9).
+
+  Note, the bootloader must configure ECC mode in the memory controller.
+
+properties:
+  compatible:
+    enum:
+      - aspeed,ast2400-sdram-edac
+      - aspeed,ast2500-sdram-edac
+      - aspeed,ast2600-sdram-edac
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    sdram@1e6e0000 {
+        compatible = "aspeed,ast2500-sdram-edac";
+        reg = <0x1e6e0000 0x174>;
+        interrupts = <0>;
+    };
diff --git a/Documentation/devicetree/bindings/edac/dmc-520.yaml b/Documentation/devicetree/bindings/edac/dmc-520.yaml
new file mode 100644
index 000000000..84db39666
--- /dev/null
+++ b/Documentation/devicetree/bindings/edac/dmc-520.yaml
@@ -0,0 +1,61 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/edac/dmc-520.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ARM DMC-520 EDAC
+
+maintainers:
+  - Lei Wang <lewan@microsoft.com>
+
+description: |+
+  DMC-520 node is defined to describe DRAM error detection and correction.
+
+  https://static.docs.arm.com/100000/0200/corelink_dmc520_trm_100000_0200_01_en.pdf
+
+properties:
+  compatible:
+    items:
+      - const: brcm,dmc-520
+      - const: arm,dmc-520
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    minItems: 1
+    maxItems: 10
+
+  interrupt-names:
+    minItems: 1
+    maxItems: 10
+    items:
+      enum:
+        - ram_ecc_errc
+        - ram_ecc_errd
+        - dram_ecc_errc
+        - dram_ecc_errd
+        - failed_access
+        - failed_prog
+        - link_err
+        - temperature_event
+        - arch_fsm
+        - phy_request
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-names
+
+additionalProperties: false
+
+examples:
+  - |
+    dmc0: dmc@200000 {
+        compatible = "brcm,dmc-520", "arm,dmc-520";
+        reg = <0x200000 0x80000>;
+        interrupts = <0x0 0x349 0x4>, <0x0 0x34B 0x4>;
+        interrupt-names = "dram_ecc_errc", "dram_ecc_errd";
+    };