sycl : fix the B70 mem allocate error when >19.3GB (llama/28953)

ggml/src/ggml-sycl/ggml-sycl.cpp

@@ -1011,12 +1011,25 @@ static size_t ggml_backend_sycl_buffer_type_get_alignment(ggml_backend_buffer_ty
     GGML_UNUSED(buft);
 }
 
+bool is_bmg_g31_arch(int device) {
+    return ggml_sycl_info().devices[device].hw_info.arch == gpu_arch::intel_gpu_bmg_g31;
+}
+
 static size_t ggml_backend_sycl_buffer_type_get_max_size(ggml_backend_buffer_type_t buft) {
     size_t max_alloc_size = dpct::get_current_device().get_max_mem_alloc_size();
     if (g_ggml_sycl_host_pinned_mem_2g) {
         return std::min(max_alloc_size, (size_t) 2LL*1024*1024*1024);
     } else {
+        ggml_backend_sycl_buffer_type_context * ctx = (ggml_backend_sycl_buffer_type_context *)buft->context;
+        int device = ctx->device;
+        if(is_bmg_g31_arch(device)) {
+            //Todo, it's workaround for BMG-G31, which has a known issue with large allocations.
+            //The max alloc size is reduced to 60% of the reported max alloc size.
+            //remove it after https://github.com/intel/compute-runtime/issues/998 is fixed.
+            max_alloc_size = max_alloc_size*0.6;
+        }
         return max_alloc_size;
+
     }
     GGML_UNUSED(buft);
 }