ci: cache QEMU binfmt image in checks job to prevent matrix cache contention

.github/actions/setup-qemu-cached/action.yaml

@@ -0,0 +1,53 @@
+name: Setup Cached QEMU
+description: Restores a cached binfmt image and installs the requested QEMU emulators
+
+inputs:
+  cache-mode:
+    description: Use prime to populate a missing cache, or restore to require it
+    default: restore
+  image:
+    description: Binfmt image to load and install
+    default: docker.io/tonistiigi/binfmt@sha256:400a4873b838d1b89194d982c45e5fb3cda4593fbfd7e08a02e76b03b21166f0 # renovate: datasource=docker depName=tonistiigi/binfmt
+  platforms:
+    description: Comma-separated emulators to install
+    default: arm64
+
+runs:
+  using: composite
+  steps:
+    - name: Restore binfmt image
+      id: cache
+      uses: actions/cache/restore@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
+      with:
+        path: ${{ runner.temp }}/qemu-binfmt
+        key: qemu-binfmt-${{ runner.os }}-${{ runner.arch }}-${{ inputs.image }}
+        fail-on-cache-miss: ${{ inputs.cache-mode == 'restore' }}
+
+    - name: Pull binfmt image
+      if: steps.cache.outputs.cache-hit != 'true'
+      shell: bash
+      env:
+        QEMU_CACHE_DIR: ${{ runner.temp }}/qemu-binfmt
+        QEMU_IMAGE: ${{ inputs.image }}
+      run: |
+        mkdir -p "$QEMU_CACHE_DIR"
+        docker pull "$QEMU_IMAGE"
+        docker save --output "$QEMU_CACHE_DIR/binfmt.tar" "$QEMU_IMAGE"
+
+    - name: Save binfmt image
+      if: steps.cache.outputs.cache-hit != 'true'
+      uses: actions/cache/save@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
+      with:
+        path: ${{ runner.temp }}/qemu-binfmt
+        key: qemu-binfmt-${{ runner.os }}-${{ runner.arch }}-${{ inputs.image }}
+
+    - name: Load binfmt image
+      shell: bash
+      run: docker load --input "${{ runner.temp }}/qemu-binfmt/binfmt.tar"
+
+    - name: Install QEMU emulators
+      shell: bash
+      env:
+        QEMU_IMAGE: ${{ inputs.image }}
+        QEMU_PLATFORMS: ${{ inputs.platforms }}
+      run: docker run --rm --privileged "$QEMU_IMAGE" --install "$QEMU_PLATFORMS"

.github/workflows/build-oss.yml

@@ -173,9 +173,7 @@ jobs:
         if: ${{ inputs.authenticated && ! inputs.full-build }}
 
       - name: Setup QEMU
-        uses: docker/setup-qemu-action@06116385d9baf250c9f4dcb4858b16962ea869c3 # v4.1.0
-        with:
-          platforms: arm64
+        uses: ./.github/actions/setup-qemu-cached
         if: ${{ steps.images_exist.outputs.base_exists != 'true' || steps.images_exist.outputs.target_exists != 'true' }}
 
       - name: Docker Buildx

.github/workflows/build-plus.yml

@@ -196,9 +196,7 @@ jobs:
         if: ${{ inputs.authenticated && ! inputs.full-build }}
 
       - name: Setup QEMU
-        uses: docker/setup-qemu-action@06116385d9baf250c9f4dcb4858b16962ea869c3 # v4.1.0
-        with:
-          platforms: arm64
+        uses: ./.github/actions/setup-qemu-cached
         if: ${{ steps.images_exist.outputs.base_exists != 'true' || steps.images_exist.outputs.target_exists != 'true' }}
 
       - name: Docker Buildx

.github/workflows/cache-update.yml

@@ -39,6 +39,11 @@ jobs:
           echo "image_matrix_nap=$(cat .github/data/matrix-images-nap.json | jq -c)" >> $GITHUB_OUTPUT
           cat $GITHUB_OUTPUT
 
+      - name: Setup QEMU
+        uses: ./.github/actions/setup-qemu-cached
+        with:
+          cache-mode: prime
+
   build-docker:
     name: Build Docker OSS
     needs: [checks]

.github/workflows/ci.yml

@@ -180,6 +180,12 @@ jobs:
           fi
           echo "run_tests=${run_tests}" >> $GITHUB_OUTPUT
 
+      - name: Setup QEMU
+        uses: ./.github/actions/setup-qemu-cached
+        with:
+          cache-mode: prime
+        if: ${{ steps.docker_build.outputs.docker_build == 'true' || steps.run_tests.outputs.run_tests == 'true' }}
+
       - name: Output variables
         run: |
           echo docs_only: ${{ github.event.pull_request && steps.docs.outputs.docs_only == 'true' }}
@@ -455,9 +461,7 @@ jobs:
         uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
 
       - name: Setup QEMU
-        uses: docker/setup-qemu-action@06116385d9baf250c9f4dcb4858b16962ea869c3 # v4.1.0
-        with:
-          platforms: arm64
+        uses: ./.github/actions/setup-qemu-cached
         if: ${{ needs.checks.outputs.forked_workflow == 'false' || needs.checks.outputs.docs_only == 'false' }}
 
       - name: Azure login