mm: add Space

src/mm/private.zig

@@ -8,10 +8,18 @@ pub const heap = @import("heap.zig");
 pub const zone = @import("zone.zig");
 pub const PMap = pmap.PMap;
 
+const ke = @import("root").ke;
+
+pub const Space = struct {
+    pmap: PMap,
+    arena: vmem.Arena,
+    lock: ke.QSpinLock,
+};
+
 pub const impl = switch (config.arch) {
     .amd64 => @import("amd64/impl.zig"),
     .um => @import("um/impl.zig"),
     else => @compileError("unsupported architecture"),
 };
 
-pub var kernel_pmap: PMap = undefined;
+pub var kernel_space: Space = undefined;