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diff --git a/llama.cpp/docs/backend/VirtGPU/configuration.md b/llama.cpp/docs/backend/VirtGPU/configuration.md new file mode 100644 index 0000000..597862d --- /dev/null +++ b/llama.cpp/docs/backend/VirtGPU/configuration.md @@ -0,0 +1,174 @@ +# GGML-VirtGPU Backend Configuration + +This document describes the environment variables used by the ggml-virtgpu backend system, covering both the frontend (guest-side) and backend (host-side) components. + +## Environment Variables Overview + +The ggml-virtgpu backend uses environment variables for configuration across three main components: +- **Frontend (Guest)**: GGML applications running in VMs +- **Hypervisor**: Virglrenderer/APIR system +- **Backend (Host)**: Host-side GGML backend integration + +## Frontend (Guest-side) Configuration + +### GGML_REMOTING_USE_APIR_CAPSET +- **Location**: `ggml/src/ggml-virtgpu/virtgpu.cpp` +- **Type**: Boolean flag (presence-based) +- **Purpose**: Controls which virtio-gpu capability set to use for communication +- **Values**: + - Set (any value): Use the APIR capset (long-term setup) + - Unset: Use the Venus capset (easier for testing with an unmodified hypervisor) +- **Default**: Unset (Venus capset) +- **Usage**: + ```bash + export GGML_REMOTING_USE_APIR_CAPSET=1 # Use APIR capset + # or leave unset for Venus capset + ``` + +## Hypervisor (Virglrenderer/APIR) Configuration + +These environment variables are used during the transition phase for +running with an unmodified hypervisor (not supporting the +VirglRenderer APIR component). They will be removed in the future, and +the hypervisor will instead configure VirglRenderer with the APIR +_Configuration Key_. + +### VIRGL_APIR_BACKEND_LIBRARY +- **Location**: `virglrenderer/src/apir/apir-context.c` +- **Configuration Key**: `apir.load_library.path` +- **Type**: File path string +- **Purpose**: Path to the APIR backend library that virglrenderer should dynamically load +- **Required**: Yes +- **Example**: + ```bash + export VIRGL_APIR_BACKEND_LIBRARY="/path/to/libggml-remotingbackend.so" + ``` + +### VIRGL_ROUTE_VENUS_TO_APIR +- **Location**: `virglrenderer/src/apir/apir-renderer.h` +- **Type**: Boolean flag (presence-based) +- **Purpose**: Temporary workaround to route Venus capset calls to APIR during hypervisor transition period +- **Status**: will be removed once hypervisors support APIR natively +- **Warning**: Breaks normal Vulkan/Venus functionality +- **Usage**: + ```bash + export VIRGL_ROUTE_VENUS_TO_APIR=1 # For testing with an unmodified hypervisor + ``` + +### VIRGL_APIR_LOG_TO_FILE +- **Location**: `virglrenderer/src/apir/apir-renderer.c` +- **Environment Variable**: `VIRGL_APIR_LOG_TO_FILE` +- **Type**: File path string +- **Purpose**: Enable debug logging from the VirglRenderer APIR component to specified file +- **Required**: No (optional debugging) +- **Default**: Logging to `stderr` +- **Usage**: + ```bash + export VIRGL_APIR_LOG_TO_FILE="/tmp/apir-debug.log" + ``` + +## Backend (Host-side) Configuration + +These environment variables are used during the transition phase for +running with an unmodified hypervisor (not supporting the +VirglRenderer APIR component). They will be removed in the future, and +the hypervisor will instead configure VirglRenderer with the APIR +_Configuration Key_. + +### APIR_LLAMA_CPP_GGML_LIBRARY_PATH +- **Location**: `ggml/src/ggml-virtgpu/backend/backend.cpp` +- **Environment Variable**: `APIR_LLAMA_CPP_GGML_LIBRARY_PATH` +- **Configuration Key**: `ggml.library.path` +- **Type**: File path string +- **Purpose**: Path to the actual GGML backend library (Metal, CUDA, Vulkan, etc.) +- **Required**: **Yes** - backend initialization fails without this +- **Examples**: + ```bash + # macOS with Metal backend + export APIR_LLAMA_CPP_GGML_LIBRARY_PATH="/opt/llama.cpp/lib/libggml-metal.dylib" + + # Linux with CUDA backend + export APIR_LLAMA_CPP_GGML_LIBRARY_PATH="/opt/llama.cpp/lib/libggml-cuda.so" + + # macOS or Linux with Vulkan backend + export APIR_LLAMA_CPP_GGML_LIBRARY_PATH="/opt/llama.cpp/lib/libggml-vulkan.so" + ``` + +### APIR_LLAMA_CPP_GGML_LIBRARY_REG +- **Location**: `ggml/src/ggml-virtgpu/backend/backend.cpp` +- **Environment Variable**: `APIR_LLAMA_CPP_GGML_LIBRARY_REG` +- **Configuration Key**: `ggml.library.reg` +- **Type**: Function symbol name string +- **Purpose**: Name of the backend registration function to call after loading the library +- **Required**: No (defaults to `ggml_backend_init`) +- **Default**: `ggml_backend_init` +- **Examples**: + ```bash + # Metal backend + export APIR_LLAMA_CPP_GGML_LIBRARY_REG="ggml_backend_metal_reg" + + # CUDA backend + export APIR_LLAMA_CPP_GGML_LIBRARY_REG="ggml_backend_cuda_reg" + + # Vulkan backend + export APIR_LLAMA_CPP_GGML_LIBRARY_REG="ggml_backend_vulkan_reg" + + # Generic fallback (default) + # export APIR_LLAMA_CPP_GGML_LIBRARY_REG="ggml_backend_init" + ``` + +### APIR_LLAMA_CPP_LOG_TO_FILE +- **Location**: `ggml/src/ggml-virtgpu/backend/backend.cpp:62` +- **Environment Variable**: `APIR_LLAMA_CPP_LOG_TO_FILE` +- **Type**: File path string +- **Purpose**: Enable debug logging from the GGML backend to specified file +- **Required**: No (optional debugging) +- **Usage**: + ```bash + export APIR_LLAMA_CPP_LOG_TO_FILE="/tmp/ggml-backend-debug.log" + ``` + +## Configuration Flow + +The configuration system works as follows: + +1. **Hypervisor Setup**: Virglrenderer loads the APIR backend library specified by `VIRGL_APIR_BACKEND_LIBRARY` + +2. **Context Creation**: When an APIR context is created, it populates a configuration table with environment variables: + - `apir.load_library.path` ← `VIRGL_APIR_BACKEND_LIBRARY` + - `ggml.library.path` ← `APIR_LLAMA_CPP_GGML_LIBRARY_PATH` + - `ggml.library.reg` ← `APIR_LLAMA_CPP_GGML_LIBRARY_REG` + - this step will eventually be performed by the hypervisor itself, with command-line arguments instead of environment variables. + +3. **Backend Initialization**: The backend queries the configuration via callbacks: + - `virgl_cbs->get_config(ctx_id, "ggml.library.path")` returns the library path + - `virgl_cbs->get_config(ctx_id, "ggml.library.reg")` returns the registration function + +4. **Library Loading**: The backend dynamically loads and initializes the specified GGML library + +## Error Messages + +Common error scenarios and their messages: + +- **Missing library path**: `"cannot open the GGML library: env var 'APIR_LLAMA_CPP_GGML_LIBRARY_PATH' not defined"` +- **Missing registration function**: `"cannot register the GGML library: env var 'APIR_LLAMA_CPP_GGML_LIBRARY_REG' not defined"` + +## Example Complete Configuration + +Here's an example configuration for a macOS host with Metal backend: + +```bash +# Hypervisor environment +export VIRGL_APIR_BACKEND_LIBRARY="/opt/llama.cpp/lib/libggml-virtgpu-backend.dylib" + +# Backend configuration +export APIR_LLAMA_CPP_GGML_LIBRARY_PATH="/opt/llama.cpp/lib/libggml-metal.dylib" +export APIR_LLAMA_CPP_GGML_LIBRARY_REG="ggml_backend_metal_reg" + +# Optional logging +export VIRGL_APIR_LOG_TO_FILE="/tmp/apir.log" +export APIR_LLAMA_CPP_LOG_TO_FILE="/tmp/ggml.log" + +# Guest configuration +export GGML_REMOTING_USE_APIR_CAPSET=1 +``` |