From 6dcbe5b3d7da688311996d8495304d560d9f493a Mon Sep 17 00:00:00 2001
From: "Else, Someone" <else@someonex.net>
Date: Thu, 9 Oct 2025 04:14:16 +0300
Subject: [PATCH] zswap in uvms: optional/configurable

---
 profiles/uvms-guest.nix | 38 +++++++++++++++++++++++++++++++++++---
 1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/profiles/uvms-guest.nix b/profiles/uvms-guest.nix
index fb9bc1c..f55e1af 100644
--- a/profiles/uvms-guest.nix
+++ b/profiles/uvms-guest.nix
@@ -7,12 +7,33 @@
 }:
 let
   mkIfGuest = import ../lib/mkIfMicrovmGuest.nix { inherit options config lib; };
+  inherit (lib) types;
 in
 {
   imports = [
     ./vsock-connect-guest.nix
     ./uvms-users.nix
   ];
+  options = {
+    uvms.zswap.enable = lib.mkEnableOption "Pass zswap.enabled=1 to kernelParams (and disable zramSwap)";
+    uvms.zswap.settings = lib.mkOption {
+      description = "Zswap kernel module configuration";
+      default = { };
+      type = types.submodule {
+        freeformType = types.attrsOf types.str;
+        options.max_pool_percent = lib.mkOption {
+          type = types.int;
+          default = 25;
+          description = "...";
+        };
+        options.compressor = lib.mkOption {
+          type = types.str;
+          default = "zstd";
+          description = "...";
+        };
+      };
+    };
+  };
   config = lib.mkMerge [
     (mkIfGuest {
       microvm = {
@@ -31,10 +52,21 @@ in
           size = 768;
         }
       ];
+      systemd.services."microvm@".serviceConfig.ExecStartPost = [
+        (pkgs.writeShellScript "microvm-fix-umask" ''
+          if [[ -e CONNECT.sock ]] ; then
+            chmod g+rw CONNECT.sock
+          fi
+        '')
+      ];
     })
-    {
-      boot.kernelParams = [ "zswap.enabled=1" ];
+    (lib.mkIf config.uvms.zswap.enable {
       zramSwap.enable = false;
-    }
+      boot.kernelParams =
+        builtins.attrValues (
+          (lib.mapAttrs (name: value: "zswap.${name}=${toString value}")) config.uvms.zswap.settings
+        )
+        ++ [ "zswap.enabled=1" ];
+    })
   ];
 }