diff --git a/nixos/doc/manual/release-notes/rl-2311.section.md b/nixos/doc/manual/release-notes/rl-2311.section.md
index 4b6335c00719..c53ada191fa2 100644
--- a/nixos/doc/manual/release-notes/rl-2311.section.md
+++ b/nixos/doc/manual/release-notes/rl-2311.section.md
@@ -589,6 +589,9 @@ The module update takes care of the new config syntax and the data itself (user
 
 - `python3.pkgs.flitBuildHook` has been removed. Use `flit-core` and `format = "pyproject"` instead.
 
+-  Now `magma` defaults to `magma-hip` instead of `magma-cuda`. It also
+   respects the `config.cudaSupport` and `config.rocmSupport` options.
+
 - The `extend` function of `llvmPackages` has been removed due it coming from the `tools` attrset thus only extending the `tool` attrset. A possible replacement is to construct the set from `libraries` and `tools`, or patch nixpkgs.
 
 - The `qemu-vm.nix` module now supports disabling overriding `fileSystems` with
diff --git a/pkgs/development/libraries/science/math/magma/generic.nix b/pkgs/development/libraries/science/math/magma/generic.nix
index 6b8588207dc3..7052b684da93 100644
--- a/pkgs/development/libraries/science/math/magma/generic.nix
+++ b/pkgs/development/libraries/science/math/magma/generic.nix
@@ -8,12 +8,7 @@
 { blas
 , cmake
 , cudaPackages
-  # FIXME: cuda being unfree means ofborg won't eval "magma".
-  # respecting config.cudaSupport -> false by default
-  # -> ofborg eval -> throws "no GPU targets specified".
-  # Probably should delete everything but "magma-cuda" and "magma-hip"
-  # from all-packages.nix
-, cudaSupport ? true
+, cudaSupport ? config.cudaSupport
 , fetchurl
 , gfortran
 , cudaCapabilities ? cudaPackages.cudaFlags.cudaCapabilities
@@ -25,7 +20,9 @@
 , magmaRelease
 , ninja
 , config
-, rocmSupport ? config.rocmSupport
+  # At least one back-end has to be enabled,
+  # and we can't default to CUDA since it's unfree
+, rocmSupport ? !cudaSupport
 , static ? false
 , stdenv
 , symlinkJoin
@@ -133,6 +130,8 @@ stdenv.mkDerivation {
 
   cmakeFlags = [
     "-DGPU_TARGET=${gpuTargetString}"
+    (lib.cmakeBool "MAGMA_ENABLE_CUDA" cudaSupport)
+    (lib.cmakeBool "MAGMA_ENABLE_HIP" rocmSupport)
   ] ++ lists.optionals static [
     "-DBUILD_SHARED_LIBS=OFF"
   ] ++ lists.optionals cudaSupport [
@@ -140,11 +139,9 @@ stdenv.mkDerivation {
     "-DMIN_ARCH=${minArch}" # Disarms magma's asserts
     "-DCMAKE_C_COMPILER=${backendStdenv.cc}/bin/cc"
     "-DCMAKE_CXX_COMPILER=${backendStdenv.cc}/bin/c++"
-    "-DMAGMA_ENABLE_CUDA=ON"
   ] ++ lists.optionals rocmSupport [
     "-DCMAKE_C_COMPILER=${rocmPackages.clr}/bin/hipcc"
     "-DCMAKE_CXX_COMPILER=${rocmPackages.clr}/bin/hipcc"
-    "-DMAGMA_ENABLE_HIP=ON"
   ];
 
   buildFlags = [
@@ -155,7 +152,7 @@ stdenv.mkDerivation {
   doCheck = false;
 
   passthru = {
-    inherit cudaPackages cudaSupport;
+    inherit cudaPackages cudaSupport rocmSupport gpuTargets;
   };
 
   meta = with lib; {
@@ -164,7 +161,11 @@ stdenv.mkDerivation {
     homepage = "http://icl.cs.utk.edu/magma/index.html";
     platforms = platforms.unix;
     maintainers = with maintainers; [ connorbaker ];
-    # CUDA and ROCm are mutually exclusive
-    broken = cudaSupport && rocmSupport || cudaSupport && strings.versionOlder cudaVersion "9";
+
+    # Cf. https://bitbucket.org/icl/magma/src/fcfe5aa61c1a4c664b36a73ebabbdbab82765e9f/CMakeLists.txt#lines-20
+    broken =
+      !(cudaSupport || rocmSupport) # At least one back-end enabled
+      || (cudaSupport && rocmSupport) # Mutually exclusive
+      || (cudaSupport && strings.versionOlder cudaVersion "9");
   };
 }
diff --git a/pkgs/development/python-modules/torch/default.nix b/pkgs/development/python-modules/torch/default.nix
index f89fed489f84..bd2ce60aab86 100644
--- a/pkgs/development/python-modules/torch/default.nix
+++ b/pkgs/development/python-modules/torch/default.nix
@@ -1,5 +1,12 @@
 { stdenv, lib, fetchFromGitHub, fetchpatch, buildPythonPackage, python,
-  config, cudaSupport ? config.cudaSupport, cudaPackages, magma,
+  config, cudaSupport ? config.cudaSupport, cudaPackages,
+  effectiveMagma ?
+  if cudaSupport then magma-cuda-static
+  else if rocmSupport then magma-hip
+  else magma,
+  magma,
+  magma-hip,
+  magma-cuda-static,
   useSystemNccl ? true,
   MPISupport ? false, mpi,
   buildDocs ? false,
@@ -115,7 +122,7 @@ let
     "CUDA is not targeting Linux" = cudaSupport && !stdenv.isLinux;
     "Unsupported CUDA version" = cudaSupport && !(builtins.elem cudaPackages.cudaMajorVersion [ "11" "12" ]);
     "MPI cudatoolkit does not match cudaPackages.cudatoolkit" = MPISupport && cudaSupport && (mpi.cudatoolkit != cudaPackages.cudatoolkit);
-    "Magma cudaPackages does not match cudaPackages" = cudaSupport && (magma.cudaPackages != cudaPackages);
+    "Magma cudaPackages does not match cudaPackages" = cudaSupport && (effectiveMagma.cudaPackages != cudaPackages);
   };
 in buildPythonPackage rec {
   pname = "torch";
@@ -359,7 +366,7 @@ in buildPythonPackage rec {
       cuda_profiler_api.dev # <cuda_profiler_api.h>
     ])
     ++ lib.optionals rocmSupport [ rocmPackages.llvm.openmp ]
-    ++ lib.optionals (cudaSupport || rocmSupport) [ magma ]
+    ++ lib.optionals (cudaSupport || rocmSupport) [ effectiveMagma ]
     ++ lib.optionals stdenv.isLinux [ numactl ]
     ++ lib.optionals stdenv.isDarwin [ Accelerate CoreServices libobjc ];
 
diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index ac993a68d9a2..583064d5e092 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -14121,10 +14121,6 @@ self: super: with self; {
   toposort = callPackage ../development/python-modules/toposort { };
 
   torch = callPackage ../development/python-modules/torch {
-    magma =
-      if pkgs.config.cudaSupport
-      then pkgs.magma-cuda-static
-      else pkgs.magma;
     inherit (pkgs.darwin.apple_sdk.frameworks) Accelerate CoreServices;
     inherit (pkgs.darwin) libobjc;
   };
@@ -14134,7 +14130,6 @@ self: super: with self; {
   };
 
   torchWithCuda = self.torch.override {
-    magma = pkgs.magma-cuda-static;
     openai-triton = self.openai-triton-cuda;
     cudaSupport = true;
     rocmSupport = false;
@@ -14145,7 +14140,6 @@ self: super: with self; {
   };
 
   torchWithRocm = self.torch.override {
-    magma = pkgs.magma-hip;
     openai-triton = self.openai-triton-no-cuda;
     rocmSupport = true;
     cudaSupport = false;