[Quantization] support logical_widths for fp8 marlin (#30962)

Signed-off-by: Jinzhen Lin <jinzhen.ljz@antgroup.com>
Signed-off-by: Jinzhen Lin <linjinzhen@hotmail.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

vllm/model_executor/layers/quantization/utils/marlin_utils_fp8.py

@@ -142,10 +142,20 @@ def prepare_fp8_layer_for_marlin(
     # marlin kernel only support channel-wise and group-wise quantization
     # we need to convert the scales
     if weight_block_size is None:
+        logical_widths = getattr(layer, "logical_widths", [])
         if scales.nelement() == 1:
             # tensor-wise quantization -> channel-wise quantization
             # (1, 1) =>(repeat)=> (1, size_n)
             scales = scales.view(1, 1).repeat_interleave(part_size_n, 1)
+        elif scales.nelement() == len(logical_widths):
+            # tensor-wise quantization with logical_widths ->
+            #    channel-wise quantization
+            assert sum(logical_widths) == part_size_n, (
+                f"Sum of logical_widths ({sum(logical_widths)}) must be equal "
+                f"to part_size_n ({part_size_n})"
+            )
+            lw_tensor = scales.new_tensor(logical_widths, dtype=torch.int64)
+            scales = scales.view(1, -1).repeat_interleave(lw_tensor, dim=1)
         elif scales.nelement() > 1 and scales.nelement() != part_size_n:
             assert part_size_n % scales.nelement() == 0
             s_size = scales.nelement()