[Bugfix][Nixl] Fix kernel physical<>logical block_size issue (#28677)

Signed-off-by: NickLucche <nlucches@redhat.com>

vllm/v1/worker/block_table.py

@@ -98,7 +98,9 @@ class BlockTable:
             return
 
         if self.use_hybrid_blocks:
-            block_ids = self._map_to_kernel_blocks(np.array(block_ids))
+            block_ids = self.map_to_kernel_blocks(
+                np.array(block_ids), self.blocks_per_kv_block, self._kernel_block_arange
+            )
 
         num_blocks = len(block_ids)
         start = self.num_blocks_per_row[row_idx]
@@ -188,7 +190,12 @@ class BlockTable:
         self.block_table.gpu.fill_(0)
         self.block_table.cpu.fill_(0)
 
-    def _map_to_kernel_blocks(self, kv_manager_block_ids: np.ndarray) -> np.ndarray:
+    @staticmethod
+    def map_to_kernel_blocks(
+        kv_manager_block_ids: np.ndarray,
+        blocks_per_kv_block: int,
+        kernel_block_arange: np.ndarray,
+    ) -> np.ndarray:
         """Convert kv_manager_block_id IDs to kernel block IDs.
 
         Example:
@@ -203,12 +210,12 @@ class BlockTable:
             # kv_manager_block_id 1 → kernel block id [2, 3]
             # kv_manager_block_id 2 → kernel block id [4, 5]
         """
-        if not self.use_hybrid_blocks:
+        if blocks_per_kv_block == 1:
             return kv_manager_block_ids
 
         kernel_block_ids = (
-            kv_manager_block_ids.reshape(-1, 1) * self.blocks_per_kv_block
-            + self._kernel_block_arange
+            kv_manager_block_ids.reshape(-1, 1) * blocks_per_kv_block
+            + kernel_block_arange
         )
 
         return kernel_block_ids.reshape(-1)