From df6e22d3393d858ba78daff5eef08ac8f7237e37 Mon Sep 17 00:00:00 2001
From: Jesse Gross <jesse@kernel.org>
Date: Tue, 3 Feb 2026 13:55:07 -0800
Subject: [PATCH 1/2] Disable managed memory on WSL when
 concurrentManagedAccess is not supported

Extend the Windows managed memory check from #3075 to also apply to WSL,
as the underlying behavior is the same.
---
 mlx/backend/cuda/allocator.cpp | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/mlx/backend/cuda/allocator.cpp b/mlx/backend/cuda/allocator.cpp
index b4ea473e9a..653183d846 100644
--- a/mlx/backend/cuda/allocator.cpp
+++ b/mlx/backend/cuda/allocator.cpp
@@ -12,6 +12,8 @@
 #include <fmt/format.h>
 
 #include <cassert>
+#include <fstream>
+#include <string>
 
 namespace mlx::core {
 
@@ -26,6 +28,29 @@ constexpr int small_block_size = 8;
 // size and small_block_size.
 constexpr int small_pool_size = 4 * page_size;
 
+// Check if running on Windows or Windows Subsystem for Linux
+bool is_windows() {
+#if defined(_WIN32)
+  return true;
+#elif defined(__linux__)
+  // WSL kernels contain "microsoft" or "WSL" in /proc/version
+  static bool is_wsl = []() {
+    std::ifstream version("/proc/version");
+    if (version.is_open()) {
+      std::string line;
+      std::getline(version, line);
+      return line.find("microsoft") != std::string::npos ||
+             line.find("Microsoft") != std::string::npos ||
+             line.find("WSL") != std::string::npos;
+    }
+    return false;
+  }();
+  return is_wsl;
+#else
+  return false;
+#endif
+}
+
 bool supports_managed_memory() {
   static bool managed_memory = []() {
     int device_count = gpu::device_count();
@@ -34,13 +59,11 @@ bool supports_managed_memory() {
       if (!d.managed_memory()) {
         return false;
       }
-#if defined(_WIN32)
-      // Empirically on Windows if there is no concurrentManagedAccess the
-      // managed memory also does not work.
-      if (!d.concurrent_managed_access()) {
+      // Empirically on Windows (and WSL) if there is no concurrentManagedAccess
+      // the managed memory also does not work.
+      if (is_windows() && !d.concurrent_managed_access()) {
         return false;
       }
-#endif
     }
     return true;
   }();

From 7f18bc4d667fa3fc56df66135f51a62d436bb739 Mon Sep 17 00:00:00 2001
From: Jesse Gross <jesse@kernel.org>
Date: Tue, 3 Feb 2026 15:04:02 -0800
Subject: [PATCH 2/2] lint

---
 mlx/backend/cuda/allocator.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mlx/backend/cuda/allocator.cpp b/mlx/backend/cuda/allocator.cpp
index 653183d846..5dcca43cde 100644
--- a/mlx/backend/cuda/allocator.cpp
+++ b/mlx/backend/cuda/allocator.cpp
@@ -40,8 +40,8 @@ bool is_windows() {
       std::string line;
       std::getline(version, line);
       return line.find("microsoft") != std::string::npos ||
-             line.find("Microsoft") != std::string::npos ||
-             line.find("WSL") != std::string::npos;
+          line.find("Microsoft") != std::string::npos ||
+          line.find("WSL") != std::string::npos;
     }
     return false;
   }();