Revert "[NVIDIA] BUMP FA3 (#11444)" (#11582)

sgl-kernel/CMakeLists.txt

@@ -90,7 +90,7 @@ FetchContent_Populate(repo-flashinfer)
 FetchContent_Declare(
     repo-flash-attention
     GIT_REPOSITORY https://github.com/sgl-project/sgl-attn
-    GIT_TAG        36f9456cd48ec57c8d75d8d6b90933d4bedffb6b
+    GIT_TAG        f9af0c2a1d82ab1812e6987e9338363cc2bf0f8d
     GIT_SHALLOW    OFF
 )
 FetchContent_Populate(repo-flash-attention)
@@ -99,7 +99,7 @@ FetchContent_Populate(repo-flash-attention)
 FetchContent_Declare(
     repo-flash-attention-origin
     GIT_REPOSITORY https://github.com/Dao-AILab/flash-attention.git
-    GIT_TAG        5a5a65b48dc99fc7483d2a7d5cfb1d8befa89389
+    GIT_TAG        203b9b3dba39d5d08dffb49c09aa622984dff07d
     GIT_SHALLOW    OFF
 )
 FetchContent_Populate(repo-flash-attention-origin)

sgl-kernel/csrc/flash_extension.cc

@@ -23,43 +23,40 @@ TORCH_LIBRARY_FRAGMENT(sgl_kernel, m) {
    * From flash-attention
    */
   m.def(
-      "fwd(Tensor   q,"                 // (b, s_q, h, d) or (total_q, h, d) if there is cu_seqlens_q
-      "    Tensor   k,"                 // (b_k, s_k, h_k, d) or (total_k, h_k, d) or paged
-      "    Tensor   v,"                 // (b_k, s_k, h_k, dv) or (total_k, h_k, dv) or paged
-      "    Tensor?  k_new,"             // (b, s_k_new, h_k, d) or (total_k_new, h_k, d)
-      "    Tensor?  v_new,"             // (b, s_k_new, h_k, dv) or (total_k_new, h_k, dv)
-      "    Tensor?  q_v,"               // (b, s_q, h, dv) or (total_q_new, h, dv)
-      "    Tensor?  out,"               // (b, s_q, h, dv) or (total_q, h, dv)
-      "    Tensor?  cu_seqlens_q,"      // b+1
-      "    Tensor?  cu_seqlens_k,"      // b+1
-      "    Tensor?  cu_seqlens_k_new,"  // b+1
-      "    Tensor?  seqused_q,"         // b
-      "    Tensor?  seqused_k,"         // b
+      "fwd(Tensor!  q,"
+      "    Tensor   k,"
+      "    Tensor   v,"
+      "    Tensor?  k_new,"
+      "    Tensor?  v_new,"
+      "    Tensor?  q_v,"
+      "    Tensor!? out,"
+      "    Tensor?  cu_seqlens_q,"
+      "    Tensor?  cu_seqlens_k,"
+      "    Tensor?  cu_seqlens_k_new,"
+      "    Tensor?  seqused_q,"
+      "    Tensor?  seqused_k,"
       "    int?     max_seqlen_q,"
-      "    int?     max_seqlen_k,"    // TODO: check if needed
-      "    Tensor?  page_table,"      // (b_k, max_num_pages_per_seq)
-      "    Tensor?  kv_batch_idx,"    // b
-      "    Tensor?  leftpad_k,"       // b
-      "    Tensor?  rotary_cos,"      // seqlen_ro x (rotary_dim / 2)
-      "    Tensor?  rotary_sin,"      // seqlen_ro x (rotary_dim / 2)
-      "    Tensor?  seqlens_rotary,"  // b
-      "    Tensor?  q_descale,"       // (b, h_k)
-      "    Tensor?  k_descale,"       // (b, h_k)
-      "    Tensor?  v_descale,"       // (b, h_k)
-      "    float?   softmax_scale,"   // now optional
+      "    int?     max_seqlen_k,"
+      "    Tensor?  page_table,"
+      "    Tensor?  kv_batch_idx,"
+      "    Tensor?  leftpad_k,"
+      "    Tensor?  rotary_cos,"
+      "    Tensor?  rotary_sin,"
+      "    Tensor?  seqlens_rotary,"
+      "    Tensor?  q_descale,"
+      "    Tensor?  k_descale,"
+      "    Tensor?  v_descale,"
+      "    float    softmax_scale,"
       "    bool     is_causal,"
       "    int      window_size_left,"
       "    int      window_size_right,"
-      "    int      attention_chunk,"  // NEW
-      "    float    softcap,"          // promoted to double in C++; schema float is fine
+      "    float    softcap,"
       "    bool     is_rotary_interleaved,"
-      "    Tensor?  scheduler_metadata,"  // (b + 1)
+      "    Tensor?  scheduler_metadata,"
       "    int      num_splits,"
       "    bool?    pack_gqa,"
       "    int      sm_margin,"
-      "    Tensor?  sinks"
-      ") -> (Tensor, Tensor, Tensor, Tensor)");  // NEW return type: tuple of 4 tensors
-
+      "    Tensor?  sinks) -> Tensor[]");
   m.impl("fwd", torch::kCUDA, make_pytorch_shim(&mha_fwd));
 }
 

sgl-kernel/include/sgl_flash_kernel_ops.h

@@ -42,44 +42,45 @@ limitations under the License.
 /*
  * From flash-attention
  */
-std::tuple<at::Tensor, at::Tensor, at::Tensor, at::Tensor> mha_fwd(
-    at::Tensor q,  // (b, s_q, h, d) or (total_q, h, d) if there is cu_seqlens_q
-    at::Tensor k,  // (b_k, s_k, h_k, d) or (total_k, h_k, d) if there is cu_seqlens_k or (num_pages, page_size,
+std::vector<at::Tensor> mha_fwd(
+    at::Tensor& q,        // (b, s_q, h, d) or (total_q, h, d) if there is cu_seqlens_q
+    const at::Tensor& k,  // (b_k, s_k, h_k, d) or (total_k, h_k, d) if there is cu_seqlens_k or (num_pages, page_size,
                           // h_k, d) if there is page_table.
-    at::Tensor v,  // (b_k, s_k, h_k, dv) or (total_k, h_k, dv) if there is cu_seqlens_k or (num_pages,
+    const at::Tensor& v,  // (b_k, s_k, h_k, dv) or (total_k, h_k, dv) if there is cu_seqlens_k or (num_pages,
                           // page_size, h_k, dv) if there is page_table.
-    std::optional<at::Tensor> k_new_,  // (b, s_k_new, h_k, d) or (total_k_new, h_k, d) if there is cu_seqlens_k_new
-    std::optional<at::Tensor> v_new_,  // (b, s_k_new, h_k, dv) or (total_k_new, h_k, dv) if there is cu_seqlens_k_new
-    std::optional<at::Tensor> q_v_,    // (b, s_q, h, dv) or (total_q_new, h, dv) if there is cu_seqlens_q
-    std::optional<at::Tensor> out_,    // (b, s_q, h, dv) or (total_q, h, dv) if there is cu_seqlens_q
-    std::optional<at::Tensor> cu_seqlens_q_,      // b+1
-    std::optional<at::Tensor> cu_seqlens_k_,      // b+1
-    std::optional<at::Tensor> cu_seqlens_k_new_,  // b+1
-    std::optional<at::Tensor>
+    std::optional<const at::Tensor>&
+        k_new_,  // (b, s_k_new, h_k, d) or (total_k_new, h_k, d) if there is cu_seqlens_k_new
+    std::optional<const at::Tensor>&
+        v_new_,  // (b, s_k_new, h_k, dv) or (total_k_new, h_k, dv) if there is cu_seqlens_k_new
+    std::optional<const at::Tensor>& q_v_,           // (b, s_q, h, dv) or (total_q_new, h, dv) if there is cu_seqlens_q
+    std::optional<at::Tensor>& out_,                 // (b, s_q, h, dv) or (total_q, h, dv) if there is cu_seqlens_q
+    std::optional<const at::Tensor>& cu_seqlens_q_,  // b+1
+    std::optional<const at::Tensor>& cu_seqlens_k_,  // b+1
+    std::optional<const at::Tensor>& cu_seqlens_k_new_,  // b+1
+    std::optional<const at::Tensor>&
         seqused_q_,  // b. If given, only this many elements of each batch element's queries and outputs are used.
-    std::optional<at::Tensor>
+    std::optional<const at::Tensor>&
         seqused_k_,  // b. If given, only this many elements of each batch element's keys are used.
-    std::optional<int64_t> max_seqlen_q_,
+    std::optional<int> max_seqlen_q_,
     // TODO: check if we need max_seqlen_k
-    std::optional<int64_t> max_seqlen_k_,
-    std::optional<at::Tensor> page_table_,      // (b_k, max_num_pages_per_seq)
-    std::optional<at::Tensor> kv_batch_idx_,    // b. indices to index into the KV cache
-    std::optional<at::Tensor> leftpad_k_,       // b
-    std::optional<at::Tensor> rotary_cos_,      // seqlen_ro x (rotary_dim / 2)
-    std::optional<at::Tensor> rotary_sin_,      // seqlen_ro x (rotary_dim / 2)
-    std::optional<at::Tensor> seqlens_rotary_,  // b
-    std::optional<at::Tensor> q_descale_,       // (b, h_k), not (b, h)
-    std::optional<at::Tensor> k_descale_,       // (b, h_k)
-    std::optional<at::Tensor> v_descale_,       // (b, h_k)
-    std::optional<double> softmax_scale_,
+    std::optional<int> max_seqlen_k_,
+    std::optional<const at::Tensor>& page_table_,      // (b_k, max_num_pages_per_seq)
+    std::optional<const at::Tensor>& kv_batch_idx_,    // b. indices to index into the KV cache
+    std::optional<const at::Tensor>& leftpad_k_,       // b
+    std::optional<const at::Tensor>& rotary_cos_,      // seqlen_ro x (rotary_dim / 2)
+    std::optional<const at::Tensor>& rotary_sin_,      // seqlen_ro x (rotary_dim / 2)
+    std::optional<const at::Tensor>& seqlens_rotary_,  // b
+    std::optional<at::Tensor>& q_descale_,             // (b, h_k), not (b, h)
+    std::optional<at::Tensor>& k_descale_,             // (b, h_k)
+    std::optional<at::Tensor>& v_descale_,             // (b, h_k)
+    float const softmax_scale,
     bool is_causal,
-    int64_t window_size_left,
-    int64_t window_size_right,
-    int64_t attention_chunk,
-    double softcap,
-    bool is_rotary_interleaved,  // if true, rotary combines indices 0 & 1, else indices 0 & rotary_dim / 2
-    std::optional<at::Tensor> scheduler_metadata_,  // (b + 1)
-    int64_t num_splits,
+    int window_size_left,
+    int window_size_right,
+    float const softcap,
+    bool const is_rotary_interleaved,  // if true, rotary combines indices 0 & 1, else indices 0 & rotary_dim / 2
+    std::optional<at::Tensor>& scheduler_metadata_,  // (b + 1)
+    int num_splits,
     std::optional<bool> pack_gqa_,
-    int64_t sm_margin,
-    std::optional<const at::Tensor>& sinks_);  // (h)
+    int const sm_margin,
+    std::optional<const at::Tensor>& sinks_);

sgl-kernel/python/sgl_kernel/flash_attn.py

@@ -43,7 +43,7 @@ def flash_attn_with_kvcache(
     qv=None,
     rotary_cos=None,
     rotary_sin=None,
-    cache_seqlens: Optional[Union[int, torch.Tensor]] = None,
+    cache_seqlens: Optional[Union[(int, torch.Tensor)]] = None,
     cache_batch_idx: Optional[torch.Tensor] = None,
     cache_leftpad: Optional[torch.Tensor] = None,
     page_table: Optional[torch.Tensor] = None,
@@ -57,7 +57,6 @@ def flash_attn_with_kvcache(
     softmax_scale=None,
     causal=False,
     window_size=(-1, -1),  # -1 means infinite context window
-    attention_chunk: Optional[int] = None,
     softcap=0.0,  # 0.0 means deactivated
     rotary_interleaved=True,
     scheduler_metadata=None,
@@ -136,7 +135,6 @@ def flash_attn_with_kvcache(
             Default to 1 / sqrt(headdim).
         causal: bool. Whether to apply causal attention mask (e.g., for auto-regressive modeling).
         window_size: (left, right). If not (-1, -1), implements sliding window local attention.
-        attention_chunk: Optional[int]. If not None, splits the query into chunks of this size to save memory.
         softcap: float. Anything > 0 activates softcapping attention.
         rotary_interleaved: bool. Only applicable if rotary_cos and rotary_sin are passed in.
             If True, rotary embedding will combine dimensions 0 & 1, 2 & 3, etc. If False,
@@ -216,7 +214,6 @@ def flash_attn_with_kvcache(
     ]
     rotary_cos, rotary_sin = [maybe_contiguous(x) for x in (rotary_cos, rotary_sin)]
     rotary_seqlens = maybe_contiguous(rotary_seqlens)
-    attention_chunk = 0 if attention_chunk is None else int(attention_chunk)
 
     out, softmax_lse, *rest = torch.ops.sgl_kernel.fwd.default(
         q,
@@ -246,7 +243,6 @@ def flash_attn_with_kvcache(
         causal,
         window_size[0],
         window_size[1],
-        attention_chunk,
         softcap,
         rotary_interleaved,
         scheduler_metadata,
@@ -276,7 +272,6 @@ def flash_attn_varlen_func(
     k_descale=None,
     v_descale=None,
     window_size=(-1, -1),
-    attention_chunk: Optional[int] = None,
     softcap=0.0,
     num_splits=1,
     pack_gqa=None,
@@ -326,7 +321,6 @@ def flash_attn_varlen_func(
         softmax_scale = (q.shape[-1] + (qv.shape[-1] if qv is not None else 0)) ** (
             -0.5
         )
-    attention_chunk = 0 if attention_chunk is None else int(attention_chunk)
 
     out, softmax_lse, *rest = torch.ops.sgl_kernel.fwd.default(
         q,
@@ -356,7 +350,6 @@ def flash_attn_varlen_func(
         causal,
         window_size[0],
         window_size[1],
-        attention_chunk,
         softcap,
         is_rotary_interleaved=False,
         scheduler_metadata=None,