From 3a76bc7a79e18020716ba063dcd1bd8ec11b0790 Mon Sep 17 00:00:00 2001
From: Peter Hoeg <peter@hoeg.com>
Date: Fri, 28 Sep 2018 22:10:03 +0800
Subject: [PATCH 1/3] nixos on hyperv: load modules and set video mode

---
 nixos/modules/virtualisation/hyperv-guest.nix | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/nixos/modules/virtualisation/hyperv-guest.nix b/nixos/modules/virtualisation/hyperv-guest.nix
index ecd2a811771..d86cb9fe1ab 100644
--- a/nixos/modules/virtualisation/hyperv-guest.nix
+++ b/nixos/modules/virtualisation/hyperv-guest.nix
@@ -9,10 +9,33 @@ in {
   options = {
     virtualisation.hypervGuest = {
       enable = mkEnableOption "Hyper-V Guest Support";
+
+      videoMode = mkOption {
+        type = types.str;
+        default = "1152x864";
+        example = "1024x768";
+        description = ''
+          Resolution at which to initialize the video adapter.
+
+          Supports screen resolution up to Full HD 1920x1080 with 32 bit color
+          on Windows Server 2012, and 1600x1200 with 16 bit color on Windows
+          Server 2008 R2 or earlier.
+        '';
+      };
     };
   };
 
   config = mkIf cfg.enable {
+    boot = {
+      initrd.kernelModules = [
+        "hv_balloon" "hv_netvsc" "hv_storvsc" "hv_utils" "hv_vmbus"
+      ];
+
+      kernelParams = [
+        "video=hyperv_fb:${cfg.videoMode}"
+      ];
+    };
+
     environment.systemPackages = [ config.boot.kernelPackages.hyperv-daemons.bin ];
 
     security.rngd.enable = false;

From ca6d41ae654386562ef7f00ae268e6e9070a3f49 Mon Sep 17 00:00:00 2001
From: Peter Hoeg <peter@hoeg.com>
Date: Fri, 28 Sep 2018 22:10:31 +0800
Subject: [PATCH 2/3] nixos-installer: use the hyperv module on hyperv

---
 nixos/modules/installer/tools/nixos-generate-config.pl | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/nixos/modules/installer/tools/nixos-generate-config.pl b/nixos/modules/installer/tools/nixos-generate-config.pl
index 359caad89a7..b70faa380e5 100644
--- a/nixos/modules/installer/tools/nixos-generate-config.pl
+++ b/nixos/modules/installer/tools/nixos-generate-config.pl
@@ -277,8 +277,7 @@ if ($virt eq "qemu" || $virt eq "kvm" || $virt eq "bochs") {
 
 # Also for Hyper-V.
 if ($virt eq "microsoft") {
-    push @initrdAvailableKernelModules, "hv_storvsc";
-    $videoDriver = "fbdev";
+    push @attrs, "virtualisation.hypervGuest.enable = true;"
 }
 
 

From 6e3e136f77b3103a0c3b3fe7578c5864932b649c Mon Sep 17 00:00:00 2001
From: Peter Hoeg <peter@hoeg.com>
Date: Fri, 28 Sep 2018 22:27:52 +0800
Subject: [PATCH 3/3] nixos on hyperv: hot-add CPU

---
 nixos/modules/virtualisation/hyperv-guest.nix | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/nixos/modules/virtualisation/hyperv-guest.nix b/nixos/modules/virtualisation/hyperv-guest.nix
index d86cb9fe1ab..0f1f052880c 100644
--- a/nixos/modules/virtualisation/hyperv-guest.nix
+++ b/nixos/modules/virtualisation/hyperv-guest.nix
@@ -40,12 +40,16 @@ in {
 
     security.rngd.enable = false;
 
-    # enable hotadding memory
+    # enable hotadding cpu/memory
     services.udev.packages = lib.singleton (pkgs.writeTextFile {
-      name = "hyperv-memory-hotadd-udev-rules";
-      destination = "/etc/udev/rules.d/99-hyperv-memory-hotadd.rules";
+      name = "hyperv-cpu-and-memory-hotadd-udev-rules";
+      destination = "/etc/udev/rules.d/99-hyperv-cpu-and-memory-hotadd.rules";
       text = ''
-        ACTION="add", SUBSYSTEM=="memory", ATTR{state}="online"
+        # Memory hotadd
+        SUBSYSTEM=="memory", ACTION=="add", DEVPATH=="/devices/system/memory/memory[0-9]*", TEST=="state", ATTR{state}="online"
+
+        # CPU hotadd
+        SUBSYSTEM=="cpu", ACTION=="add", DEVPATH=="/devices/system/cpu/cpu[0-9]*", TEST=="online", ATTR{online}="1"
       '';
     });