CUDA: Support CUDA Virtual Devices

.github/workflows/server-self-hosted.yml

@@ -143,6 +143,24 @@ jobs:
           export LLAMA_ARG_BACKEND_SAMPLING=1
           pytest -v -x -m "not slow"
 
+      - name: Tests (GPUx2)
+        id: server_integration_tests_gpu2
+        if: ${{ !github.event.pull_request }}
+        run: |
+          cd tools/server/tests
+          source venv/bin/activate
+          export GGML_CUDA_DEVICES=2
+          pytest -v -x -m "not slow"
+
+      - name: Tests (GPUx2, backend-sampling)
+        id: server_integration_tests_gpu2_backend_sampling
+        if: ${{ !github.event.pull_request }}
+        run: |
+          cd tools/server/tests
+          source venv/bin/activate
+          export GGML_CUDA_DEVICES=2 LLAMA_ARG_BACKEND_SAMPLING=1
+          pytest -v -x -m "not slow"
+
   server-kleidiai:
     runs-on: ah-ubuntu_22_04-c8g_8x
 

ggml/src/ggml-cuda/common.cuh

@@ -1115,7 +1115,8 @@ struct ggml_cuda_type_traits<GGML_TYPE_IQ3_S> {
 //////////////////////
 
 struct ggml_cuda_device_info {
-    int device_count;
+    int device_count;           // number of (possibly virtual) devices exposed to the rest of ggml
+    int physical_device_count;  // number of physical CUDA devices actually present
 
     struct cuda_device_info {
         int     cc;                             // compute capability
@@ -1128,6 +1129,9 @@ struct ggml_cuda_device_info {
         size_t  total_vram;
         int     warp_size;                      // Number of threads in a dispatch
         bool    supports_cooperative_launch;    // whether cooperative launch is supported
+        int     physical_device;                // backing physical CUDA device for this (virtual) device
+        int     physical_share_count;           // number of (virtual) devices sharing this device's physical GPU
+        int     virtual_index;                  // index of this (virtual) device among those sharing its physical GPU
     };
 
     cuda_device_info devices[GGML_CUDA_MAX_DEVICES] = {};