Initial vmtests

This is broken due to the init script spawning qemu-ga which fails under
the nix flake environment

TODO:
- separate vmtests infra in a different file
- add more kernels

.github/workflows/vmtest.yml

@@ -0,0 +1,31 @@
+name: vmtests
+
+on:
+    pull_request:
+    push:
+
+jobs:
+  vmtests:
+    runs-on: ubuntu-22.04
+    permissions:
+        id-token: write
+        contents: read
+
+    steps:
+    - uses: actions/checkout@main
+    - uses: DeterminateSystems/nix-installer-action@main
+    - uses: DeterminateSystems/magic-nix-cache-action@main
+
+    - name: Install system deps
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y qemu-system-x86-64 qemu-guest-agent qemu-utils ovmf
+
+    - name: Set up nix dev env
+      run: nix develop --command echo 0
+
+    - name: Build `lightswitch` statically linked using glibc
+      run: nix develop --command bash -c 'RUSTFLAGS="-C target-feature=+crt-static" cargo build --release --target x86_64-unknown-linux-gnu'
+
+    - name: Run vmtests
+      run: nix develop --command run-vmtests

.gitignore

@@ -1,3 +1,4 @@
 /target
 flame.svg
 src/bpf/*_skel.rs
+.vmtest.log

flake.nix

@@ -21,6 +21,100 @@
           elfutils-without-zstd = pkgs.elfutils.overrideAttrs (attrs: {
             configureFlags = attrs.configureFlags ++ [ "--without-zstd" ];
           });
+          # Separate in other nix files.
+          kernel_5_15 = pkgs.stdenv.mkDerivation {
+            name = "download-kernel-5.15";
+            src = pkgs.fetchurl {
+              url = "https://github.com/danobi/vmtest/releases/download/test_assets/bzImage-v5.15-fedora38";
+              hash = "sha256-nq8W72vuNKCgO1OS6aJtAfg7AjHavRZ7WAkP7X6V610=";
+            };
+            dontUnpack = true;
+            installPhase = ''
+              mkdir -p $out
+              cp -r $src $out/bzImage
+            '';
+          };
+
+          kernel_6_6 = pkgs.stdenv.mkDerivation {
+            name = "download-kernel-6.6";
+            src = pkgs.fetchurl {
+              url = "https://github.com/danobi/vmtest/releases/download/test_assets/bzImage-v6.6-fedora38";
+              hash = "sha256-6Fu16SPBITP0sI3lapkckZna6GKBn2hID038itt82jA=";
+            };
+            dontUnpack = true;
+            installPhase = ''
+              mkdir -p $out
+              cp -r $src $out/bzImage
+            '';
+          };
+
+          # Using the rust derivation to make nix aware of this package and use the cache.
+          vmtest = pkgs.rustPlatform.buildRustPackage {
+            name = "vmtest";
+            src = pkgs.fetchFromGitHub {
+              owner = "danobi";
+              repo = "vmtest";
+              rev = "51f11bf301fea054342996802a16ed21fb5054f4";
+              sha256 = "sha256-qtTq0dnDHi1ITfQzKrXz+1dRMymAFBivWpjXntD09+A=";
+            };
+            cargoHash = "sha256-SHjjCWz4FVVk1cczkMltRVEB3GK8jz2tVABNSlSZiUc=";
+            nativeCheckInputs = [ pkgs.qemu ];
+
+            # There are various errors trying to access `/build/source/tests/*`.
+            doCheck = false;
+
+            meta = with pkgs.lib; {
+              description = "Helps run tests in virtual machines";
+              homepage = "https://github.com/danobi/vmtest/";
+              license = licenses.asl20;
+              mainProgram = "";
+              maintainers = with maintainers; [ ];
+              platforms = platforms.linux;
+            };
+          };
+
+
+          vmtest-create-config = pkgs.stdenv.mkDerivation {
+            name = "vmtest-dump-config";
+            dontUnpack = true;
+
+            # The flamegraph is written to the current directory, run lightswitch from /tmp to write it there.
+            src = pkgs.writeText "vmtest.toml" ''
+              [[target]]
+              name = "Fedora 5.15"
+              kernel = "${kernel_5_15.out}/bzImage"
+              command = "pushd /tmp && /home/javierhonduco/code/lightswitch/target/x86_64-unknown-linux-gnu/debug/lightswitch --duration 2"
+
+              [[target]]
+              name = "Fedora 6.6"
+              kernel = "${kernel_6_6.out}/bzImage"
+              command = "pushd /tmp && /home/javierhonduco/code/lightswitch/target/x86_64-unknown-linux-gnu/debug/lightswitch --duration 2"
+            '';
+            nativeBuildInputs = [ vmtest kernel_5_15 kernel_6_6 ];
+            installPhase = ''
+              mkdir -p $out
+              cp -r $src $out/vmtest.toml
+            '';
+          };
+
+          # Requires lightswitch to be statically built using the x86_64-unknown-linux-gnu target. Definitely
+          # should be done automatically.
+          runvmtests = pkgs.stdenv.mkDerivation {
+            name = "run-vmtests";
+            dontUnpack = true;
+
+            src = pkgs.writeText "run-vmtests" ''
+              ${vmtest}/bin/vmtest --config ${vmtest-create-config}/vmtest.toml
+            '';
+            # propagatedBuildInputs = [ pkgs.qemu ];
+            nativeBuildInputs = [ vmtest-create-config ];
+            installPhase = ''
+              mkdir -p $out/bin
+              cp -r $src $out/bin/run-vmtests
+              chmod +x $out/bin/run-vmtests
+            '';
+          };
+
         in
         with pkgs;
         {
@@ -38,6 +132,7 @@
               llvmPackages_16.libcxx
               llvmPackages_16.libclang
               llvmPackages_16.lld
+              runvmtests
               # Debugging
               strace
               gdb