minor fixes

Signed-off-by: Charlene Yang <8636796+cyanguwa@users.noreply.github.com>

transformer_engine/pytorch/attention.py

@@ -348,7 +348,7 @@ def get_attention_backend(
         use_fused_attention = False
 
     # Filter: Compute capability
-    global _flash_attn_3_plus, _use_flash_attn_3
+    global _use_flash_attn_3
     if device_compute_capability < (8, 0):
         if use_flash_attention:
             logger.debug("Disabling FlashAttention as it requires compute capability sm80+")
@@ -357,7 +357,7 @@ def get_attention_backend(
             logger.debug("Disabling FusedAttention as it requires compute capability sm80+")
             use_fused_attention = False
     if device_compute_capability < (9, 0):
-        if use_flash_attention and _flash_attn_3_plus:
+        if use_flash_attention and _use_flash_attn_3:
             logger.debug("Disabling FlashAttention 3 as it requires compute capability sm90+")
             _use_flash_attn_3 = False
 
@@ -436,15 +436,11 @@ def get_attention_backend(
                 "padding between sequences, i.e. [a, a, PAD, b, b, b, PAD, c, PAD]"
             )
             use_flash_attention = False
-        if use_flash_attention and _use_flash_attn_3 and fp8 and fp8_meta["recipe"].fp8_dpa:
-            logger.debug("Disabling FlashAttention 3 for FP8 and qkv_format = thd")
-            _use_flash_attn_3 = False
 
     # Filter: Dropout
-    if attention_dropout != 0.0 and use_flash_attention:
-        if _flash_attn_3_plus and _use_flash_attn_3:
-            logger.debug("Disabling FlashAttention 3 for dropout")
-            _use_flash_attn_3 = False
+    if attention_dropout != 0.0 and use_flash_attention and _use_flash_attn_3:
+        logger.debug("Disabling FlashAttention 3 for dropout")
+        _use_flash_attn_3 = False
 
     # Filter: Context parallelism
     # qkv_format | attn_mask_type              | attn_bias_type           | supported backends
@@ -464,7 +460,7 @@ def get_attention_backend(
         )
         use_unfused_attention = False
     if context_parallel and use_flash_attention:
-        if _flash_attn_3_plus and _use_flash_attn_3:
+        if _use_flash_attn_3:
             logger.debug("Disabling FlashAttention 3 for context parallelism")
             _use_flash_attn_3 = False
         if fp8 and fp8_meta["recipe"].fp8_dpa:
@@ -559,7 +555,7 @@ def get_attention_backend(
         use_fused_attention = False
     if (
         use_flash_attention
-        and _flash_attn_3_plus
+        and _use_flash_attn_3
         and attn_mask_type in ["causal", "padding_causal"]
         and max_seqlen_q != max_seqlen_kv
     ):
@@ -593,6 +589,9 @@ def get_attention_backend(
             "https://github.com/Dao-AILab/flash-attention#21-change-behavior-of-causal-flag"
         )
         use_flash_attention = False
+    if use_flash_attention and _use_flash_attn_3 and fp8 and fp8_meta["recipe"].fp8_dpa and "padding" in attn_mask_type:
+        logger.debug("Disabling FlashAttention 3 for FP8 and padding masks")
+        _use_flash_attn_3 = False
 
     # Filter: Sliding window attention
     #    backend                 |      window_size       | diagonal alignment
@@ -656,12 +655,12 @@ def get_attention_backend(
     # UnfusedDotProductAttention | no_bias, pre/post_scale_bias |
     #                            | alibi/alibi_slopes           | both; converts to a 'post_scale_bias' bias
     if use_flash_attention and core_attention_bias_type == "alibi":
-        if _flash_attn_3_plus and _use_flash_attn_3:
+        if _use_flash_attn_3:
             logger.debug("Disabling FlashAttention 3 for ALiBi")
             _use_flash_attn_3 = False
-            if not _flash_attn_2_4_plus:
-                logger.debug("Disabling FlashAttention for ALiBi")
-                use_flash_attention = False
+        elif not _flash_attn_2_4_plus:
+            logger.debug("Disabling FlashAttention as ALiBi requires flash-attn 2.4+")
+            use_flash_attention = False
 
     if use_flash_attention and (
         core_attention_bias_type not in ["no_bias", "alibi"]
@@ -5011,7 +5010,7 @@ def forward(
                 if _flash_attn_2_4_1_plus:
                     fa_optional_forward_kwargs["deterministic"] = self.deterministic
                 fa_optional_forward_args_thd = []
-                if (qkv_format in ["bshd", "sbhd"] and "padding" not in attn_mask_type) or fp8:
+                if qkv_format in ["bshd", "sbhd"] and "padding" not in attn_mask_type:
                     func = flash_attn_func if not _use_flash_attn_3 else flash_attn_func_v3
                 else:
                     if _flash_attn_2_5_7_plus: