3 files changed, 41 insertions, 2 deletions
diff --git a/nixos/modules/hardware/cpu/amd-microcode.nix b/nixos/modules/hardware/cpu/amd-microcode.nix
index d44f01a49590..621c7066bfe1 100644
--- a/nixos/modules/hardware/cpu/amd-microcode.nix
+++ b/nixos/modules/hardware/cpu/amd-microcode.nix
@@ -22,7 +22,8 @@ with lib;
   ###### implementation
 
   config = mkIf config.hardware.cpu.amd.updateMicrocode {
-    boot.initrd.prepend = [ "${pkgs.microcodeAmd}/amd-ucode.img" ];
+    # Microcode updates must be the first item prepended in the initrd
+    boot.initrd.prepend = mkOrder 1 [ "${pkgs.microcodeAmd}/amd-ucode.img" ];
   };
 
 }
diff --git a/nixos/modules/hardware/cpu/intel-microcode.nix b/nixos/modules/hardware/cpu/intel-microcode.nix
index 89ae4f45806c..acce565fd808 100644
--- a/nixos/modules/hardware/cpu/intel-microcode.nix
+++ b/nixos/modules/hardware/cpu/intel-microcode.nix
@@ -22,7 +22,8 @@ with lib;
   ###### implementation
 
   config = mkIf config.hardware.cpu.intel.updateMicrocode {
-    boot.initrd.prepend = [ "${pkgs.microcodeIntel}/intel-ucode.img" ];
+    # Microcode updates must be the first item prepended in the initrd
+    boot.initrd.prepend = mkOrder 1 [ "${pkgs.microcodeIntel}/intel-ucode.img" ];
   };
 
 }
diff --git a/nixos/modules/hardware/mcelog.nix b/nixos/modules/hardware/mcelog.nix
new file mode 100644
index 000000000000..e4ac7d39053f
--- /dev/null
+++ b/nixos/modules/hardware/mcelog.nix
@@ -0,0 +1,37 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  meta.maintainers = [ maintainers.grahamc ];
+  options = {
+
+    hardware.mcelog = {
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Enable the Machine Check Exception logger.
+        '';
+      };
+    };
+
+  };
+
+  config = mkIf config.hardware.mcelog.enable {
+    systemd.services.mcelog = {
+      description = "Machine Check Exception Logging Daemon";
+      wantedBy = [ "multi-user.target" ];
+
+      serviceConfig = {
+        ExecStart = "${pkgs.mcelog}/bin/mcelog --daemon --foreground";
+        SuccessExitStatus = [ 0 15 ];
+
+        ProtectHome = true;
+        PrivateNetwork = true;
+        PrivateTmp = true;
+      };
+    };
+  };
+
+}