Do not loose string context unless the nix store is on a disk

Author: SuperSandro2000

lib/runners/alioth.nix

@@ -31,7 +31,7 @@ in {
         "--num-cpu" (toString vcpu)
         "-k" (lib.escapeShellArg "${kernel}/${pkgs.stdenv.hostPlatform.linux-kernel.target}")
         "-i" initrdPath
-        "-c" (lib.escapeShellArg "console=ttyS0 reboot=k panic=1 ${builtins.unsafeDiscardStringContext (toString microvmConfig.kernelParams)}")
+        "-c" (lib.escapeShellArg "console=ttyS0 reboot=k panic=1 ${toString microvmConfig.kernelParams}")
         "--entropy"
       ]
       ++

lib/runners/cloud-hypervisor.nix

@@ -35,7 +35,7 @@ let
 
   kernelConsole = lib.optionalString (!hasUserSerial || userSerial == "tty") kernelConsoleDefault;
 
-  kernelCmdLine = "${kernelConsole} reboot=t panic=-1 ${builtins.unsafeDiscardStringContext (toString microvmConfig.kernelParams)}";
+  kernelCmdLine = "${kernelConsole} reboot=t panic=-1 ${toString microvmConfig.kernelParams}";
 
 
   userVSockOpts = (extractOptValues "--vsock" extraArgs).values;

lib/runners/crosvm.nix

@@ -61,7 +61,7 @@ in {
         "-m" (toString mem)
         "-c" (toString vcpu)
         "--serial" "type=stdout,console=true,stdin=true"
-        "-p" "console=ttyS0 reboot=k panic=1 ${builtins.unsafeDiscardStringContext (toString microvmConfig.kernelParams)}"
+        "-p" "console=ttyS0 reboot=k panic=1 ${toString microvmConfig.kernelParams}"
       ]
       ++
       lib.optional (!balloon) "--no-balloon"

lib/runners/firecracker.nix

@@ -23,7 +23,7 @@ let
     boot-source = {
       kernel_image_path = kernelPath;
       initrd_path = initrdPath;
-      boot_args = "console=ttyS0 noapic acpi=off reboot=k panic=1 i8042.noaux i8042.nomux i8042.nopnp i8042.dumbkbd ${builtins.unsafeDiscardStringContext (toString microvmConfig.kernelParams)}";
+      boot_args = "console=ttyS0 noapic acpi=off reboot=k panic=1 i8042.noaux i8042.nomux i8042.nopnp i8042.dumbkbd ${toString microvmConfig.kernelParams}";
     };
     machine-config = {
       vcpu_count = vcpu;

lib/runners/kvmtool.nix

@@ -37,7 +37,7 @@ in {
         "--rng"
         "-k" (lib.escapeShellArg "${kernel}/${pkgs.stdenv.hostPlatform.linux-kernel.target}")
         "-i" initrdPath
-        "-p" (lib.escapeShellArg "console=ttyS0 reboot=k panic=1 ${builtins.unsafeDiscardStringContext (toString microvmConfig.kernelParams)}")
+        "-p" (lib.escapeShellArg "console=ttyS0 reboot=k panic=1 ${toString microvmConfig.kernelParams}")
       ]
       ++
       lib.optionals storeOnDisk [

lib/runners/qemu.nix

@@ -209,10 +209,10 @@ lib.warnIf (mem == 2048) ''
     lib.optionals (system == "x86_64-linux") [
       "-device" "i8042"
 
-      "-append" "${kernelConsole} reboot=t panic=-1 ${builtins.unsafeDiscardStringContext (toString microvmConfig.kernelParams)}"
+      "-append" "${kernelConsole} reboot=t panic=-1 ${toString microvmConfig.kernelParams}"
     ] ++
     lib.optionals (system == "aarch64-linux") [
-      "-append" "${kernelConsole} reboot=t panic=-1 ${builtins.unsafeDiscardStringContext (toString microvmConfig.kernelParams)}"
+      "-append" "${kernelConsole} reboot=t panic=-1 ${toString microvmConfig.kernelParams}"
     ] ++
     lib.optionals storeOnDisk [
       "-drive" "id=store,format=raw,read-only=on,file=${storeDisk},if=none,aio=${aioEngine}"

lib/runners/stratovirt.nix

@@ -92,7 +92,7 @@ in {
 
       "-kernel" "${kernel}/bzImage"
       "-initrd" initrdPath
-      "-append" "console=${console} edd=off reboot=t panic=-1 ${builtins.unsafeDiscardStringContext (toString microvmConfig.kernelParams)}"
+      "-append" "console=${console} edd=off reboot=t panic=-1 ${toString microvmConfig.kernelParams}"
 
       "-serial" "stdio"
       "-object" "rng-random,id=rng,filename=/dev/random"

nixos-modules/microvm/store-disk.nix

@@ -1,9 +1,14 @@
 { config, lib, pkgs, ... }:
 
 let
-  regInfo = pkgs.closureInfo {
-    rootPaths = [ config.system.build.toplevel ];
-  };
+  regInfo = let
+    regInfo' = pkgs.closureInfo {
+      rootPaths = [ config.system.build.toplevel ];
+    };
+  in if config.microvm.storeOnDisk then
+    builtins.unsafeDiscardStringContext regInfo'
+  else
+    regInfo';
 
   erofs-utils =
     # Are any extended options specified?

nixos-modules/microvm/system.nix

@@ -28,8 +28,13 @@
       "overlay"
     ];
 
-    microvm.kernelParams = config.boot.kernelParams ++ [
-      "init=${config.system.build.toplevel}/init"
+    microvm.kernelParams = let
+      toplevel = if config.microvm.storeOnDisk then
+        builtins.unsafeDiscardStringContext config.system.build.toplevel;
+      else
+        config.system.build.toplevel
+    in config.boot.kernelParams ++ [
+      "init=${toplevel}/init"
     ];
 
     # modules that consume boot time but have rare use-cases