From bfa3be010c8c90f1bd0326747b9b424535381bb2 Mon Sep 17 00:00:00 2001
From: pacien
Date: Sat, 12 Nov 2022 03:52:06 +0100
Subject: mkSandboxSystem: add option for qemu 9p perf patch

---
 lib/mk-sandbox-system.nix | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/lib/mk-sandbox-system.nix b/lib/mk-sandbox-system.nix
index bbe0238..7514b93 100644
--- a/lib/mk-sandbox-system.nix
+++ b/lib/mk-sandbox-system.nix
@@ -4,6 +4,7 @@
 , user ? "dummy"
 , config ? { }
 , restrictNetwork ? true  # to be replaced with virtualisation.restrictNetwork
+, patchQemu9p ? false
 }:
 
 with nixpkgs.lib;
@@ -11,6 +12,18 @@ with nixpkgs.lib;
 let
   pkgs = import nixpkgs { inherit system; };
 
+  # Patched QEMU to fix slow 9p file share.
+  # https://linus.schreibt.jetzt/posts/qemu-9p-performance.html
+  qemu_kvm_patched_9p =
+  assert !(pkgs.lib.versionAtLeast pkgs.qemu_kvm.version "7.2.0");
+  pkgs.qemu_kvm.overrideAttrs (o: {
+    patches = o.patches ++ [ (pkgs.fetchpatch {
+      name = "qemu-9p-performance-fix.patch";
+      url = "https://github.com/qemu/qemu/commit/f5265c8.patch";
+      sha256 = "sha256-PSOv0dhiEq9g6B1uIbs6vbhGr7BQWCtAoLHnk4vnvVg=";
+    }) ];
+  });
+
 in rec {
 
   nixosConfigurations.${name} = nixosSystem {
@@ -60,6 +73,9 @@ in rec {
           # Uncomment when this is merged:
           # https://github.com/NixOS/nixpkgs/pull/200225
           #restrictNetwork = mkDefault true;
+
+          qemu.package = mkDefault
+            (if patchQemu9p then qemu_kvm_patched_9p else pkgs.qemu_kvm);
         };
       })
 
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