ci: incorporate the pr feedback

.github/workflows/ci.yml

@@ -106,40 +106,41 @@ jobs:
         working-directory: kernel
     strategy:
       matrix:
-        arch: ["x86_64", "aarch64"]
-        release-profile: ["--dev", "--release"]
-        demo: ["rusty_demo", "httpd", "httpd-rtl8139", "testudp", "microvm"]
+        arch: [x86_64, aarch64]
+        profile: [dev, release]
+        package: [rusty_demo, httpd, testudp, hello_world]
+        netdev: [virtio-net-pci, rtl8139]
         include:
-          - arch: "x86_64"
-            packages: "qemu-system-x86 libcap-ng-dev libseccomp-dev socat"
-          - arch: "aarch64"
-            packages: "qemu-system-aarch64"
+          - arch: x86_64
+            packages: qemu-system-x86 libcap-ng-dev libseccomp-dev socat
+          - arch: aarch64
+            packages: qemu-system-aarch64
 
-            # Demos that do not share a name with the corresponding package
-          - demo: "httpd-rtl8139"
-            package: "httpd"
-          - demo: "microvm"
-            package: "hello_world"
-
-          - arch: "x86_64"
-            demo: "rusty_demo"
-            flags: "--features pci-ids --virtiofsd"
-          - arch: "aarch64"
-            demo: "rusty_demo"
-            flags: "--features pci-ids"
-          - demo: "httpd"
-            flags: "--features ci,dhcpv4 --netdev virtio-net-pci"
-          - demo: "httpd-rtl8139"
-            flags: "--features ci,dhcpv4,rtl8139 --netdev rtl8139"
-          - demo: "microvm"
-            flags: "--no-default-features --microvm"
-          - demo: "testudp"
-            flags: "--features udp,dhcpv4 --netdev virtio-net-pci"
+          - arch: x86_64
+            package: rusty_demo
+            flags: --features pci-ids --virtiofsd
+          - arch: aarch64
+            package: rusty_demo
+            flags: --features pci-ids
+          - package: httpd
+            flags: --features ci,dhcpv4
+          - package: testudp
+            flags: --features udp,dhcpv4
+          - package: hello_world
+            flags: --no-default-features --microvm
         exclude:
-          - arch: "aarch64"
-            demo: "httpd-rtl8139"
-          - arch: "aarch64"
-            demo: "microvm"
+          # rtl8139 does not build on aarch64
+          - arch: aarch64
+            netdev: rtl8139
+          # microvm (Firecracker) test does not run on aarch64
+          - package: hello_world
+            arch: aarch64
+          # The rusty_demo and microvm tests ignore the netdev, so we exclude all but one netdev to prevent redundant jobs.
+          # We choose rtl8139 to not build an unnecessary feature into the build
+          - package: hello_world
+            netdev: rtl8139
+          - package: rusty_demo
+            netdev: rtl8139
 
     steps:
       - name: Checkout hermit-rs
@@ -176,8 +177,17 @@ jobs:
         if: ${{ matrix.arch == 'x86_64' && matrix.demo == 'rusty_demo' }}
         run: cargo install virtiofsd
       - name: Run VM
-        # The package name is the same as the demo name if not explicitly specified
-        run: cargo xtask ci qemu --arch ${{ matrix.arch }} --package ${{ matrix.package || matrix.demo }} ${{ matrix.flags }}
+        # cargo accepts multiple 'features' flags
+        # The '… && … || …' expression is like a ternary operator
+        # netdev is only relevant for tests that use network functionality (and are thus built with dhcpv4)
+        run: >
+              cargo xtask ci qemu
+              --arch ${{ matrix.arch }}
+              --package ${{ matrix.package }}
+              ${{ matrix.flags }}
+              ${{ matrix.netdev == 'rtl8139' && '--features rtl8139' || '' }}
+              ${{ contains(matrix.flags, 'dhcpv4') && format('--netdev {0}', matrix.netdev) ||  '' }}
+              --${{ matrix.profile }}
 
   run-x86_64-kvm:
     name: Run Hermit for Rust (x86_64 + kvm)