kleidiai : warn once when a weight type has no KleidiAI kernel (#25701)

ggml/src/ggml-cpu/kleidiai/kleidiai.cpp

@@ -1719,6 +1719,7 @@ class extra_buffer_type : ggml::cpu::extra_buffer_type {
 
             return true;
         }
+
         return false;
     }
 
@@ -1727,6 +1728,20 @@ class extra_buffer_type : ggml::cpu::extra_buffer_type {
             if (op->src[0]->buffer && op->src[0]->buffer->buft == ggml_backend_cpu_kleidiai_buffer_type()) {
                 return (ggml::cpu::tensor_traits *) op->src[0]->extra;
             } else {
+                // KleidiAI only has kernels for Q4_0 and Q8_0. For a quantized weight of any
+                // other type (K-quants, IQ) it declines the op and returns nullptr below, so
+                // KleidiAI does not accelerate it. Another CPU backend may still take the op,
+                // and this can run during graph planning, so the message says what KleidiAI
+                // did rather than what ends up executing. Warn once per process.
+                if (ggml_is_quantized(op->src[0]->type) &&
+                    op->src[0]->type != GGML_TYPE_Q4_0 && op->src[0]->type != GGML_TYPE_Q8_0) {
+                    static std::atomic<bool> warned(false);
+                    if (!warned.exchange(true)) {
+                        GGML_LOG_WARN("kleidiai: no kernel for tensor type %s, not accelerated by KleidiAI "
+                                      "(kernels available for Q4_0 and Q8_0)\n",
+                                      ggml_type_name(op->src[0]->type));
+                    }
+                }
                 if (op->src[0]->type != GGML_TYPE_F16) {
                     return nullptr;
                 }