From 157a1cf990cb7be414e102dff9faddc93b35425e Mon Sep 17 00:00:00 2001
From: Manuel Thalmann <m@nuth.ch>
Date: Wed, 8 May 2024 11:13:07 +0200
Subject: [PATCH] Allow enabling USB redirection

---
 lib/configuration.nix           |  1 +
 lib/modules/custom-build-vm.nix | 29 ++++++++++++++++++++++++++---
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/lib/configuration.nix b/lib/configuration.nix
index 749995a..1138829 100644
--- a/lib/configuration.nix
+++ b/lib/configuration.nix
@@ -15,6 +15,7 @@
         vmConfig = {
           virtualisation = {
             sharedHostKeys = true;
+            usb-redirect = true;
             virt-viewer = true;
             cores = 4;
             memorySize = 4 * 1024;
diff --git a/lib/modules/custom-build-vm.nix b/lib/modules/custom-build-vm.nix
index 00936a2..422ce6c 100644
--- a/lib/modules/custom-build-vm.nix
+++ b/lib/modules/custom-build-vm.nix
@@ -36,6 +36,12 @@ in {
           default = false;
         };
 
+        usb-redirect = lib.mkOption {
+          type = lib.types.bool;
+          description = lib.mdDoc "Whether to enable USB redirection to the VM.";
+          default = false;
+        };
+
         virt-viewer = lib.mkOption {
           type = lib.types.bool;
           description = "Whether to use `remote-viewer` for displaying the VM.";
@@ -84,7 +90,9 @@ in {
 
             virtualisation = {
               # Enable root permissions to get access to the `/etc/ssh` directory
-              runAsRoot = lib.mkIf vmVariant.virtualisation.sharedHostKeys true;
+              runAsRoot = lib.mkIf
+                (vmVariant.virtualisation.sharedHostKeys || vmVariant.virtualisation.usb-redirect)
+                true;
 
               # Enable spice and run QEMU in background to let `remote-viewer` take over
               qemu = {
@@ -94,7 +102,22 @@ in {
                 options =
                   with {
                     inherit (vmVariant.virtualisation.qemu) spice;
+                    inherit (vmVariant.virtualisation) usb-redirect;
                   };
+                  (
+                    lib.optionals usb-redirect (
+                      [
+                        "-usb"
+                        "-device qemu-xhci"
+                      ] ++ (builtins.concatMap
+                        (index:
+                          let
+                            devName = "usbredirchardev${toString index}";
+                          in [
+                            "-chardev spicevmc,name=usbredir,id=${devName}"
+                            "-device usb-redir,chardev=${devName},id=usbredirdev${toString index}"
+                          ])
+                        (lib.lists.range 1 3)))) ++
                   (
                     lib.optional (spice.enable)
                       ("-spice " + (
@@ -147,6 +170,7 @@ in {
 
                 vmRunner = pkgs.writeShellApplication {
                   name = "run-${config.system.name}-vm";
+                  runtimeInputs = lib.optional config.virtualisation.usb-redirect pkgs.spice-gtk;
 
                   text = lib.strings.concatLines (
                     [
@@ -159,10 +183,9 @@ in {
                             let
                               spice = config.virtualisation.qemu.spice;
                               remoteAddress = "spice://${lib.escapeShellArg spice.bindAddress}:${toString spice.port}";
-                              viewerPrefix = "sudo -Eu\"#$SUDO_UID\" ";
                             in
                               [
-                                "${viewerPrefix}${pkgs.virt-viewer}/bin/remote-viewer ${remoteAddress}"
+                                "${pkgs.virt-viewer}/bin/remote-viewer ${remoteAddress}"
                                 # Kill QEMU after `remote-viewer` finished running
                                 "kill %1"
                               ]))));