ggml: new backend for Virglrenderer API Remoting acceleration (v2) (#18718)

ggml/src/ggml-virtgpu/virtgpu-forward-backend.cpp

@@ -0,0 +1,50 @@
+#include "virtgpu-forward-impl.h"
+
+static long long current_time_ms() {
+    timespec ts;
+    clock_gettime(CLOCK_REALTIME, &ts);  // Use CLOCK_MONOTONIC for elapsed time
+    return (long long) ts.tv_sec * 1000000000LL + ts.tv_nsec;
+}
+
+ggml_status apir_backend_graph_compute(virtgpu * gpu, ggml_cgraph * cgraph) {
+    apir_encoder *        encoder;
+    apir_decoder *        decoder;
+    ApirForwardReturnCode ret;
+
+    REMOTE_CALL_PREPARE(gpu, encoder, APIR_COMMAND_TYPE_BACKEND_GRAPH_COMPUTE);
+
+    std::vector<uint8_t> cgraph_data;
+    size_t               cgraph_size = apir_serialize_ggml_cgraph(cgraph, cgraph_data);
+
+    virtgpu_shmem   temp_shmem;  // Local storage for large buffers
+    virtgpu_shmem * shmem = &temp_shmem;
+
+    if (cgraph_size <= gpu->data_shmem.mmap_size) {
+        // prefer the init-time allocated page, if large enough
+        shmem = &gpu->data_shmem;
+    } else if (virtgpu_shmem_create(gpu, cgraph_size, shmem)) {
+        GGML_ABORT("Couldn't allocate the guest-host shared buffer");
+    }
+
+    apir_encode_virtgpu_shmem_res_id(encoder, shmem->res_id);
+
+    apir_encode_size_t(encoder, &cgraph_size);
+
+    char *       shmem_data    = (char *) shmem->mmap_ptr;
+    apir_encoder secondary_enc = apir_new_encoder(shmem_data, cgraph_size);
+
+    apir_encode_cgraph_data(&secondary_enc, cgraph_data);
+
+    REMOTE_CALL(gpu, encoder, decoder, ret);
+
+    ggml_status status = GGML_STATUS_ABORTED;
+    apir_decode_ggml_status(decoder, &status);
+
+    remote_call_finish(gpu, encoder, decoder);
+
+    if (shmem != &gpu->data_shmem) {
+        virtgpu_shmem_destroy(gpu, shmem);
+    }
+
+    return status;
+}