From ef5268bcab5d5272a8622bf429ece73dd3fe05c1 Mon Sep 17 00:00:00 2001
From: Mira Ressel <aranea@aixah.de>
Date: Tue, 1 Sep 2020 17:00:14 +0200
Subject: [PATCH 1/3] nixos/qemu-vm: Fix condition in requiredKernelConfig

'optional' just takes a single item rather than a list
---
 nixos/modules/virtualisation/qemu-vm.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/nixos/modules/virtualisation/qemu-vm.nix b/nixos/modules/virtualisation/qemu-vm.nix
index 191d7c758c0..068d448c933 100644
--- a/nixos/modules/virtualisation/qemu-vm.nix
+++ b/nixos/modules/virtualisation/qemu-vm.nix
@@ -751,7 +751,7 @@ in
         (isYes "NET_CORE")
         (isYes "INET")
         (isYes "NETWORK_FILESYSTEMS")
-      ] ++ optional (!cfg.graphics) [
+      ] ++ optionals (!cfg.graphics) [
         (isYes "SERIAL_8250_CONSOLE")
         (isYes "SERIAL_8250")
       ];

From 8ee970442b27d7163ca218d58c763309fccded3c Mon Sep 17 00:00:00 2001
From: Mira Ressel <aranea@aixah.de>
Date: Tue, 1 Sep 2020 17:05:36 +0200
Subject: [PATCH 2/3] nixos/qemu-vm: Don't require CONFIG_EXPERIMENTAL

The kernel stopped using this config option with version 3.9 (back in
2013!).
---
 nixos/modules/virtualisation/qemu-vm.nix | 1 -
 1 file changed, 1 deletion(-)

diff --git a/nixos/modules/virtualisation/qemu-vm.nix b/nixos/modules/virtualisation/qemu-vm.nix
index 068d448c933..7534fd744fd 100644
--- a/nixos/modules/virtualisation/qemu-vm.nix
+++ b/nixos/modules/virtualisation/qemu-vm.nix
@@ -746,7 +746,6 @@ in
         (isEnabled "EXT4_FS")
         (isYes "BLK_DEV")
         (isYes "PCI")
-        (isYes "EXPERIMENTAL")
         (isYes "NETDEVICES")
         (isYes "NET_CORE")
         (isYes "INET")

From a7de454a762cd6bda49a33c8531a553d67bce231 Mon Sep 17 00:00:00 2001
From: Mira Ressel <aranea@aixah.de>
Date: Tue, 1 Sep 2020 17:08:01 +0200
Subject: [PATCH 3/3] nixos/qemu-vm: Update system.requiredKernelConfig

Verify that all kernel modules which are required for mounting
/nix/store in the VM are present.
---
 nixos/modules/virtualisation/qemu-vm.nix | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/nixos/modules/virtualisation/qemu-vm.nix b/nixos/modules/virtualisation/qemu-vm.nix
index 7534fd744fd..33da920e94c 100644
--- a/nixos/modules/virtualisation/qemu-vm.nix
+++ b/nixos/modules/virtualisation/qemu-vm.nix
@@ -744,6 +744,8 @@ in
         (isEnabled "VIRTIO_PCI")
         (isEnabled "VIRTIO_NET")
         (isEnabled "EXT4_FS")
+        (isEnabled "NET_9P_VIRTIO")
+        (isEnabled "9P_FS")
         (isYes "BLK_DEV")
         (isYes "PCI")
         (isYes "NETDEVICES")
@@ -753,6 +755,8 @@ in
       ] ++ optionals (!cfg.graphics) [
         (isYes "SERIAL_8250_CONSOLE")
         (isYes "SERIAL_8250")
+      ] ++ optionals (cfg.writableStore) [
+        (isEnabled "OVERLAY_FS")
       ];
 
   };