ci: refactor toolchain setup

The 'toolchain' matrix parameter has been used in a confusing way. The
'version' field was only applicable to LLVM, but there is also a
separate 'llvm-version' action parameter spread across the workflows.

Now that we want to be able to specify a particular GCC version for
kernel build, a refactoring is appropriate.

Given that libbpf/ci/setup-build-env action sets up a particular
compiler version systemwide, and mixing LLVM versions between kernel
and selftests build is an unlikely scenario, it makes sense to simply
have gcc_version and llvm_version parameter, fixed within a particular
workflow. And so the composite 'toolchain' becomes unnecessary: it's
enough to distinguish between gcc and llvm build of the kernel.

However 'toolchain' and 'toolchain_full' are still useful variables
between the workflows and actions, particularly for identifying build
artifacts.

Here is what happens now:
  * DEFAULT_{GCC,LLVM}_VERSION is set in matrix.py
  * 'toolchain' is replaced with 'kernel_compiler' in the job matrix
  * test.yml workflow looks at kernel_compiler to construct and pass
   'toolchain' and 'toolchain_full' to other workflows
  * '{gcc,llvm}_version' inputs are used to determine compiler
    versions for the build setup

Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>

Author: theihor

.github/scripts/matrix.py

@@ -16,6 +16,7 @@
 
 DEFAULT_SELF_HOSTED_RUNNER_TAGS: Final[List[str]] = ["self-hosted", "docker-noble-main"]
 DEFAULT_GITHUB_HOSTED_RUNNER: Final[str] = "ubuntu-24.04"
+DEFAULT_GCC_VERSION: Final[int] = 13
 DEFAULT_LLVM_VERSION: Final[int] = 17
 
 RUNNERS_BUSY_THRESHOLD: Final[float] = 0.8
@@ -36,31 +37,6 @@ class Compiler(str, Enum):
     LLVM = "llvm"
 
 
-@dataclasses.dataclass
-class Toolchain:
-    compiler: Compiler
-    # This is relevant ONLY for LLVM and should not be required for GCC
-    version: int
-
-    @property
-    def short_name(self) -> str:
-        return str(self.compiler.value)
-
-    @property
-    def full_name(self) -> str:
-        if self.compiler == Compiler.GCC:
-            return self.short_name
-
-        return f"{self.short_name}-{self.version}"
-
-    def to_dict(self) -> Dict[str, Union[str, int]]:
-        return {
-            "name": self.short_name,
-            "fullname": self.full_name,
-            "version": self.version,
-        }
-
-
 def query_runners_from_github() -> List[Dict[str, Any]]:
     if "GITHUB_TOKEN" not in os.environ:
         return []
@@ -150,7 +126,9 @@ def count_by_status(runners: List[Dict[str, Any]]) -> Dict[str, int]:
 @dataclasses.dataclass
 class BuildConfig:
     arch: Arch
-    toolchain: Toolchain
+    kernel_compiler: Compiler = Compiler.GCC
+    gcc_version: int = DEFAULT_GCC_VERSION
+    llvm_version: int = DEFAULT_LLVM_VERSION
     kernel: str = "LATEST"
     run_veristat: bool = False
     parallel_tests: bool = False
@@ -205,7 +183,7 @@ def tests(self) -> Dict[str, Any]:
         if self.arch.value != "s390x":
             tests_list.append("test_maps")
 
-        if self.toolchain.version >= 18:
+        if self.llvm_version >= 18:
             tests_list.append("test_progs_cpuv4")
 
         # if self.arch in [Arch.X86_64, Arch.AARCH64]:
@@ -224,7 +202,9 @@ def tests(self) -> Dict[str, Any]:
     def to_dict(self) -> Dict[str, Any]:
         return {
             "arch": self.arch.value,
-            "toolchain": self.toolchain.to_dict(),
+            "kernel_compiler": self.kernel_compiler.value,
+            "gcc_version": DEFAULT_GCC_VERSION,
+            "llvm_version": DEFAULT_LLVM_VERSION,
             "kernel": self.kernel,
             "run_veristat": self.run_veristat,
             "parallel_tests": self.parallel_tests,
@@ -272,27 +252,19 @@ def generate_test_config(test: str) -> Dict[str, Union[str, int]]:
     matrix = [
         BuildConfig(
             arch=Arch.X86_64,
-            toolchain=Toolchain(compiler=Compiler.GCC, version=DEFAULT_LLVM_VERSION),
             run_veristat=True,
             parallel_tests=True,
         ),
         BuildConfig(
             arch=Arch.X86_64,
-            toolchain=Toolchain(compiler=Compiler.LLVM, version=DEFAULT_LLVM_VERSION),
-            build_release=True,
-        ),
-        BuildConfig(
-            arch=Arch.X86_64,
-            toolchain=Toolchain(compiler=Compiler.LLVM, version=18),
+            kernel_compiler=Compiler.LLVM,
             build_release=True,
         ),
         BuildConfig(
             arch=Arch.AARCH64,
-            toolchain=Toolchain(compiler=Compiler.GCC, version=DEFAULT_LLVM_VERSION),
         ),
         BuildConfig(
             arch=Arch.S390X,
-            toolchain=Toolchain(compiler=Compiler.GCC, version=DEFAULT_LLVM_VERSION),
         ),
     ]
 

.github/workflows/gcc-bpf.yml

@@ -9,7 +9,10 @@ on:
       arch:
         required: true
         type: string
-      llvm-version:
+      gcc_version:
+        required: true
+        type: string
+      llvm_version:
         required: true
         type: string
       toolchain:
@@ -75,10 +78,11 @@ jobs:
         run: zstd -d -T0 vmlinux-${{ inputs.arch }}-${{ inputs.toolchain_full }}.tar.zst --stdout | tar -xf -
 
       - name: Setup build environment
-        uses: libbpf/ci/setup-build-env@v3
+        uses: theihor/libbpf-ci/setup-build-env@gcc-14
         with:
           arch: ${{ inputs.arch }}
-          llvm-version: ${{ inputs.llvm-version }}
+          gcc-version: ${{ inputs.gcc_version }}
+          llvm-version: ${{ inputs.llvm_version }}
 
       - name: Download GCC BPF compiler
         shell: bash
@@ -95,6 +99,5 @@ jobs:
         with:
           arch: ${{ inputs.arch }}
           kernel-root: ${{ env.REPO_ROOT }}
-          llvm-version: ${{ inputs.llvm-version }}
+          llvm-version: ${{ inputs.llvm_version }}
           toolchain: ${{ inputs.toolchain }}
-

.github/workflows/kernel-build-test.yml

@@ -23,10 +23,14 @@ on:
         required: true
         type: string
         description: The runners to run the builds on. This is a json string representing an array of labels.
-      llvm-version:
+      gcc_version:
         required: true
         type: string
-        description: The version of LLVM used to build selftest.... for llvm toolchain, this should match the one from toolchain_full, for gcc it is an arbritrary version we decide to build selftests against.
+        description: GCC version to install
+      llvm_version:
+        required: true
+        type: string
+        description: LLVM version to install
       kernel:
         required: true
         type: string
@@ -67,7 +71,8 @@ jobs:
       toolchain_full: ${{ inputs.toolchain_full }}
       toolchain: ${{ inputs.toolchain }}
       runs_on: ${{ inputs.build_runs_on }}
-      llvm-version: ${{ inputs.llvm-version }}
+      gcc_version: ${{ inputs.gcc_version }}
+      llvm_version: ${{ inputs.llvm_version }}
       kernel: ${{ inputs.kernel }}
       download_sources: ${{ inputs.download_sources }}
 
@@ -79,7 +84,8 @@ jobs:
       toolchain_full: ${{ inputs.toolchain_full }}
       toolchain: ${{ inputs.toolchain }}
       runs_on: ${{ inputs.build_runs_on }}
-      llvm-version: ${{ inputs.llvm-version }}
+      gcc_version: ${{ inputs.gcc_version }}
+      llvm_version: ${{ inputs.llvm_version }}
       kernel: ${{ inputs.kernel }}
       download_sources: ${{ inputs.download_sources }}
       release: true
@@ -112,7 +118,7 @@ jobs:
       contents: read
     with:
       arch: ${{ inputs.arch }}
-      toolchain: ${{ inputs.toolchain }}
+      toolchain_full: ${{ inputs.toolchain_full }}
       runs_on: ${{ inputs.runs_on }}
 
   veristat-meta:
@@ -125,7 +131,7 @@ jobs:
       contents: read
     with:
       arch: ${{ inputs.arch }}
-      toolchain: ${{ inputs.toolchain }}
+      toolchain_full: ${{ inputs.toolchain_full }}
       aws_region: ${{ vars.AWS_REGION }}
       runs_on: ${{ inputs.runs_on }}
     secrets:
@@ -140,7 +146,8 @@ jobs:
       # GCC BPF does not need /dev/kvm, so use the "build" runners
       runs_on: ${{ inputs.build_runs_on }}
       arch: ${{ inputs.arch }}
-      llvm-version: ${{ inputs.llvm-version }}
+      gcc_version: ${{ inputs.gcc_version }}
+      llvm_version: ${{ inputs.llvm_version }}
       toolchain: ${{ inputs.toolchain }}
       toolchain_full: ${{ inputs.toolchain_full }}
       download_sources: ${{ inputs.download_sources }}

.github/workflows/kernel-build.yml

@@ -20,10 +20,14 @@ on:
         required: true
         type: string
         description: The runners to run the test on. This is a json string representing an array of labels.
-      llvm-version:
+      gcc_version:
         required: true
         type: string
-        description: The version of LLVM used to build selftest.... for llvm toolchain, this should match the one from toolchain_full, for gcc it is an arbritrary version we decide to build selftests against.
+        description: GCC version to install
+      llvm_version:
+        required: true
+        type: string
+        description: LLVM version to install
       kernel:
         required: true
         type: string
@@ -41,7 +45,7 @@ on:
 
 jobs:
   build:
-    name: build for ${{ inputs.arch }} with ${{ inputs.toolchain_full }}${{ inputs.release && '-O2' || '' }}
+    name: build kernel and selftests ${{ inputs.release && '-O2' || '' }}
     # To run on CodeBuild, runs-on value must correspond to the AWS
     # CodeBuild project associated with the kernel-patches webhook
     # However matrix.py passes just a 'codebuild' string
@@ -106,10 +110,11 @@ jobs:
           repo-root: ${{ env.REPO_ROOT }}
 
       - name: Setup build environment
-        uses: libbpf/ci/setup-build-env@v3
+        uses: theihor/libbpf-ci/setup-build-env@gcc-14
         with:
           arch: ${{ inputs.arch }}
-          llvm-version: ${{ inputs.llvm-version }}
+          gcc-version: ${{ inputs.gcc_version }}
+          llvm-version: ${{ inputs.llvm_version }}
           pahole: master
 
         # We have to setup qemu+binfmt in order to enable cross-compation of selftests.
@@ -131,7 +136,7 @@ jobs:
           toolchain: ${{ inputs.toolchain }}
           kbuild-output: ${{ env.KBUILD_OUTPUT }}
           max-make-jobs: 32
-          llvm-version: ${{ inputs.llvm-version }}
+          llvm-version: ${{ inputs.llvm_version }}
 
       - name: Build selftests/bpf
         uses: libbpf/ci/build-selftests@v3
@@ -141,7 +146,7 @@ jobs:
         with:
           arch: ${{ inputs.arch }}
           kernel-root: ${{ env.KERNEL_ROOT }}
-          llvm-version: ${{ inputs.llvm-version }}
+          llvm-version: ${{ inputs.llvm_version }}
           toolchain: ${{ inputs.toolchain }}
 
       - if: ${{ env.BUILD_SCHED_EXT_SELFTESTS }}
@@ -152,7 +157,7 @@ jobs:
           repo-root: ${{ env.REPO_ROOT }}
           arch: ${{ inputs.arch }}
           toolchain: ${{ inputs.toolchain }}
-          llvm-version: ${{ inputs.llvm-version }}
+          llvm-version: ${{ inputs.llvm_version }}
           max-make-jobs: 32
 
       - if: ${{ github.event_name != 'push' }}
@@ -163,7 +168,7 @@ jobs:
           toolchain: ${{ inputs.toolchain }}
           kbuild-output: ${{ env.KBUILD_OUTPUT }}
           max-make-jobs: 32
-          llvm-version: ${{ inputs.llvm-version }}
+          llvm-version: ${{ inputs.llvm_version }}
       - name: Tar artifacts
         id: tar-artifacts
         uses: libbpf/ci/tar-artifacts@v3

.github/workflows/test.yml

@@ -44,7 +44,7 @@ jobs:
   build-and-test:
     # Setting name to arch-compiler here to avoid lengthy autogenerated names due to matrix
     # e.g build-and-test x86_64-gcc / test (test_progs_parallel, true, 30) / test_progs_parallel on x86_64 with gcc
-    name: "${{ matrix.arch }}-${{ matrix.toolchain.fullname }}"
+    name: ${{ matrix.arch }} ${{ matrix.kernel_compiler }}-${{ matrix.kernel_compiler == 'gcc' && matrix.gcc_version || matrix.llvm_version }}
     uses: ./.github/workflows/kernel-build-test.yml
     needs: [set-matrix]
     permissions:
@@ -55,11 +55,12 @@ jobs:
       matrix: ${{ fromJSON(needs.set-matrix.outputs.build-matrix) }}
     with:
       arch: ${{ matrix.arch }}
-      toolchain_full: ${{ matrix.toolchain.fullname }}
-      toolchain: ${{ matrix.toolchain.name }}
+      toolchain: ${{ matrix.kernel_compiler }}
+      toolchain_full: ${{ matrix.kernel_compiler }}-${{ matrix.kernel_compiler == 'gcc' && matrix.gcc_version || matrix.llvm_version }}
       runs_on: ${{ toJSON(matrix.runs_on) }}
       build_runs_on: ${{ toJSON(matrix.build_runs_on) }}
-      llvm-version: ${{ matrix.toolchain.version }}
+      gcc_version: ${{ matrix.gcc_version }}
+      llvm_version: ${{ matrix.llvm_version }}
       kernel: ${{ matrix.kernel }}
       tests: ${{ toJSON(matrix.tests) }}
       run_veristat: ${{ matrix.run_veristat }}

.github/workflows/veristat-kernel.yml

@@ -7,18 +7,18 @@ on:
         required: true
         type: string
         description: The architecture to build against, e.g x86_64, aarch64, s390x...
-      toolchain:
+      toolchain_full:
         required: true
         type: string
-        description: The toolchain, e.g gcc, llvm
+        description: Toolchain identifier, such as llvm-20
       runs_on:
         required: true
         type: string
         description: The runners to run the test on. This is a json string representing an array of labels.
 
 jobs:
   veristat:
-    name: ${{ inputs.arch }}-${{ inputs.toolchain }} veristat_kernel
+    name: veristat-kernel
     runs-on: ${{ fromJSON(inputs.runs_on) }}
     timeout-minutes: 100
     permissions:
@@ -29,7 +29,7 @@ jobs:
       REPO_ROOT: ${{ github.workspace }}
       REPO_PATH: ""
       KBUILD_OUTPUT: kbuild-output/
-      ARCH_AND_TOOL: ${{ inputs.arch }}-${{ inputs.toolchain }}
+      ARCH_AND_TOOL: ${{ inputs.arch }}-${{ inputs.toolchain_full }}
 
     steps:
 

.github/workflows/veristat-meta.yml

@@ -7,10 +7,10 @@ on:
         required: true
         type: string
         description: The architecture to build against, e.g x86_64, aarch64, s390x...
-      toolchain:
+      toolchain_full:
         required: true
         type: string
-        description: The toolchain, e.g gcc, llvm
+        description: Toolchain identifier, such as llvm-20
       runs_on:
         required: true
         type: string
@@ -26,7 +26,7 @@ on:
 
 jobs:
   veristat:
-    name: ${{ inputs.arch }}-${{ inputs.toolchain }} veristat_meta
+    name: veristat-meta
     runs-on: ${{ fromJSON(inputs.runs_on) }}
     timeout-minutes: 100
     permissions:
@@ -37,7 +37,7 @@ jobs:
       REPO_ROOT: ${{ github.workspace }}
       REPO_PATH: ""
       KBUILD_OUTPUT: kbuild-output/
-      ARCH_AND_TOOL: ${{ inputs.arch }}-${{ inputs.toolchain }}
+      ARCH_AND_TOOL: ${{ inputs.arch }}-${{ inputs.toolchain_full }}
 
     steps: