[Attention] Deepseek v3 MLA support with FP8 compute (#12601)

This PR implements the Deepseek V3 support by performing matrix absorption the fp8 weights 

---------
Signed-off-by: Lucas Wilkinson <lwilkinson@neuralmagic.com>
Co-authored-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>
Co-authored-by: simon-mo <simon.mo@hey.com>
Co-authored-by: Michael Goin <mgoin64@gmail.com>
Co-authored-by: Zhuohan Li <zhuohan123@gmail.com>
Co-authored-by: Tyler Michael Smith <tysmith@redhat.com>
Co-authored-by: Alexander Matveev <59768536+alexm-neuralmagic@users.noreply.github.com>

vllm/attention/backends/mla/utils.py

 from abc import abstractmethod
 from dataclasses import dataclass
-from typing import Any, Dict, Generic, List, Optional
+from typing import Any, Dict, Generic, List, Optional, Tuple
 
 import torch
+from compressed_tensors.quantization import QuantizationStrategy
 
 from vllm import _custom_ops as ops
 from vllm import envs
 from vllm.attention.backends.abstract import (AttentionLayer,
                                               AttentionMetadata,
                                               MLAAttentionImpl, T)
-from vllm.distributed import get_tensor_model_parallel_world_size
+from vllm.distributed import (get_tensor_model_parallel_world_size,
+                              tensor_model_parallel_all_reduce)
 from vllm.model_executor.layers.linear import (ColumnParallelLinear,
-                                               RowParallelLinear)
+                                               LinearBase, RowParallelLinear,
+                                               UnquantizedLinearMethod)
+from vllm.model_executor.layers.quantization.compressed_tensors.compressed_tensors import (  # noqa: E501
+    CompressedTensorsLinearMethod)
+from vllm.model_executor.layers.quantization.compressed_tensors.schemes import (
+    CompressedTensorsW8A8Fp8)
+from vllm.model_executor.layers.quantization.fp8 import Fp8LinearMethod
+from vllm.model_executor.layers.quantization.utils.fp8_utils import (
+    apply_fp8_linear_generic, current_platform_fp8_dtype, is_fp8)
+from vllm.model_executor.layers.quantization.utils.quant_utils import (
+    scaled_dequantize, scaled_quantize)
 from vllm.model_executor.layers.rotary_embedding import RotaryEmbedding
 from vllm.vllm_flash_attn import flash_attn_varlen_func
 
@@ -25,11 +37,11 @@ class MLACommonMetadata(AttentionMetadata):
 
 class MLACommonImpl(MLAAttentionImpl[T], Generic[T]):
     """
-    Common class for implementing repeated parts 
-    
+    Common class for implementing repeated parts
+
     Main reference: DeepseekV2 paper, and FlashInfer Implementation
     (https://arxiv.org/abs/2405.04434 and https://github.com/flashinfer-ai/flashinfer/pull/551).
-    
+
     Deepseek's MLA attention works the following way:
     * Use a single latent vector to represent the entire KV cache.
     * The attention "simulates" a multi-head attention, while the compute is
@@ -46,7 +58,7 @@ class MLACommonImpl(MLAAttentionImpl[T], Generic[T]):
         * V: V head dim.
         * kv_c: latent/compressed KV
         * q_c: latent/compressed Q
-        
+
         #
         # Outside the MLA attention backend
         #
@@ -55,21 +67,21 @@ class MLACommonImpl(MLAAttentionImpl[T], Generic[T]):
            kv_c_k_pe (B, Lkv+R).
         2. The kv_c_k_pe is split into kv_c (B, Lkv) and k_pe (B, R). cq
            and kv_c are normalized.
-        
+
         #
         # Inside the MLA attention backend
         #
 
         * if prefill:
-        
-        3. The q_c is then projected up into the multi-head version. 
-           * q_c goes from (B, Lq) to (B, N, (P+R)), which is split into q_nope 
-             (B, N, P) and q_pe (B, N, R). 
+
+        3. The q_c is then projected up into the multi-head version.
+           * q_c goes from (B, Lq) to (B, N, (P+R)), which is split into q_nope
+             (B, N, P) and q_pe (B, N, R).
         4. q_pe, k_pe are then passed through rotary embeddings.
         5. kv_c and k_pe are concatenated and inserted into the cache
-        6. The kv_c is then projected up into the multi-head version. 
-           * kv_c goes from (B, Lkv) to (B, N, (P+V)) which has the nope 
-             dimensions for K and V, which is split into k_nope (B, N, P) 
+        6. The kv_c is then projected up into the multi-head version.
+           * kv_c goes from (B, Lkv) to (B, N, (P+V)) which has the nope
+             dimensions for K and V, which is split into k_nope (B, N, P)
              and v (B, N, V).
         7. q (B, N, (P+R)) and k (B, N, (P+R)) matrices are assembled from
            q_nope, q_pe, k_nope, k_pe.
@@ -112,7 +124,7 @@ class MLACommonImpl(MLAAttentionImpl[T], Generic[T]):
     From @tsu-bin's calculation, we only want to use the absorption technique
     for decode. The prefill algorithm should still use the up-projected MHA
     for less flops and memory usage.
-    
+
     """
 
     def __init__(
@@ -162,8 +174,19 @@ class MLACommonImpl(MLAAttentionImpl[T], Generic[T]):
 
     def _v_up_proj_and_o_proj(self, x):
         if envs.VLLM_MLA_PERFORM_MATRIX_ABSORPTION:
-            return self.o_proj_absorbed(
-                x.reshape(-1, self.num_heads * self.kv_lora_rank))[0]
+            if is_fp8(self.W_UV_O):
+                output_parallel = apply_fp8_linear_generic(
+                    x.flatten(start_dim=1), self.W_UV_O, self.W_UV_O_scales,
+                    self.reqaunt_input_group_shape,
+                    self.reqaunt_weight_group_shape)
+            else:
+                output_parallel = torch.matmul(x.flatten(start_dim=1),
+                                               self.W_UV_O)
+            if self.tp_size > 1:
+                output = tensor_model_parallel_all_reduce(output_parallel)
+            else:
+                output = output_parallel
+            return output
         else:
             x = torch.einsum("bnl,lnv->bnv", x, self.W_UV)
             return self.o_proj(x.reshape(-1,
@@ -171,6 +194,12 @@ class MLACommonImpl(MLAAttentionImpl[T], Generic[T]):
 
     def _q_proj_and_k_up_proj(self, x):
         if envs.VLLM_MLA_PERFORM_MATRIX_ABSORPTION:
+            if is_fp8(self.W_Q_UK):
+                return apply_fp8_linear_generic(
+                    x, self.W_Q_UK, self.W_Q_UK_scales,
+                    self.reqaunt_input_group_shape,
+                    self.reqaunt_weight_group_shape).view(
+                        -1, self.num_heads, self.kv_lora_rank)
             return torch.matmul(x, self.W_Q_UK)\
                 .view(-1, self.num_heads, self.kv_lora_rank)
         else:
@@ -179,8 +208,91 @@ class MLACommonImpl(MLAAttentionImpl[T], Generic[T]):
             return torch.einsum("bnp,lnp->bnl", x, self.W_UK)\
                 .view(-1, self.num_heads, self.kv_lora_rank)
 
-    def process_weights_after_loading(self):
-        kv_b_proj_weight = self.kv_b_proj.weight.T
+    def process_weights_after_loading(self, act_dtype: torch.dtype):
+
+        def is_layer_fp8(layer: LinearBase) -> bool:
+            return isinstance(layer.quant_method, Fp8LinearMethod) or\
+                (isinstance(layer.quant_method, CompressedTensorsLinearMethod)\
+                and isinstance(layer.scheme, CompressedTensorsW8A8Fp8))
+
+        def quantization_scheme_supported(layer: LinearBase) -> bool:
+            return isinstance(layer.quant_method, UnquantizedLinearMethod) or \
+                is_layer_fp8(layer)
+
+        # TODO(lucas) This is very gross, we need a more wide scale refactor of
+        # all the FP8 code with a more standard way of
+        # defining schemes/group-shapes, we should also potentially force
+        # quant_methods to support a decompress function
+        #
+        # returns input_group_shape, weight_group_shape
+        def get_scale_group_shapes_for_fp8(layer: LinearBase) -> \
+            Tuple[Tuple[int, int], Tuple[int, int]]:
+            if isinstance(layer.quant_method, Fp8LinearMethod):
+                if layer.quant_method.block_quant is not None:
+                    weight_block_size = \
+                        layer.quant_method.quant_config.weight_block_size
+                    # per-token-group (1, X), block-quantized (X, Y)
+                    return (1, weight_block_size[-1]), weight_block_size
+                else:
+                    return (-1, -1), (-1, -1)  # per-tensor, per-tensor
+            elif isinstance(layer.quant_method, CompressedTensorsLinearMethod)\
+                and isinstance(layer.scheme, CompressedTensorsW8A8Fp8):
+                # this is hacky but we always assume the for
+                # CompressedTensorsW8A8Fp8 the input is dynamic per-token
+                # we ignore if it is static-per-tensor since we are going to
+                # requantize after later anyways
+                strategy = layer.scheme.strategy
+                if strategy == QuantizationStrategy.TENSOR:
+                    return (1, -1), (-1, -1)  # per-token, per-tensor
+                elif strategy == QuantizationStrategy.CHANNEL:
+                    return (1, -1), (-1, 1)  # per-token, per-channel
+                else:
+                    raise NotImplementedError(
+                        f"QuantizationStrategy.{strategy} is not supported for "
+                        "fp8 MLA, please run with VLLM_MLA_DISABLE=1")
+            else:
+                raise NotImplementedError(
+                    "Can't determine scale group shapes for "
+                    f"{layer.quant_method}, please run with VLLM_MLA_DISABLE=1"
+                )
+
+        def get_scales(layer: LinearBase) -> torch.Tensor:
+            if hasattr(layer, "weight_scale_inv"):
+                return layer.weight_scale_inv
+            return layer.weight_scale
+
+        def get_and_maybe_dequant_weights(layer: LinearBase):
+            if is_layer_fp8(layer):
+                if isinstance(layer.quant_method, \
+                    CompressedTensorsLinearMethod) and \
+                    isinstance(layer.scheme, CompressedTensorsW8A8Fp8):
+                    # NOTE(lucas): note sure why but `CompressedTensorsW8A8Fp8`
+                    # seems to store weights as (input, output) instead of
+                    # (output, input) so we need to transpose
+                    weight = layer.weight.T  # standardize to (output, input)
+                else:
+                    weight = layer.weight
+                _, weight_scale_group_shape = \
+                    get_scale_group_shapes_for_fp8(layer)
+                scales = get_scales(layer)
+
+                return scaled_dequantize(weight, scales,
+                                         weight_scale_group_shape)
+            else:
+                return layer.weight
+
+        if not (quantization_scheme_supported(self.kv_b_proj) and\
+            quantization_scheme_supported(self.q_proj) and\
+                quantization_scheme_supported(self.o_proj)):
+            raise NotImplementedError(
+                "Only FP8 and UnquantizedLinearMethod are supported for MLA"
+                ", please run with VLLM_MLA_DISABLE=1")
+
+        weight_dtype = self.kv_b_proj.weight.dtype
+        assert self.o_proj.weight.dtype == weight_dtype
+        assert self.q_proj.weight.dtype == weight_dtype
+
+        kv_b_proj_weight = get_and_maybe_dequant_weights(self.kv_b_proj).T
         assert kv_b_proj_weight.shape == (
             self.kv_lora_rank,
             self.num_heads * (self.qk_nope_head_dim + self.v_head_dim)), (
@@ -198,18 +310,35 @@ class MLACommonImpl(MLAAttentionImpl[T], Generic[T]):
         W_UK, W_UV = kv_b_proj_weight.split(
             [self.qk_nope_head_dim, self.v_head_dim], dim=-1)
 
-        q_proj = self.q_proj.weight.T\
+        q_proj_weight = get_and_maybe_dequant_weights(self.q_proj).T\
                 .view(-1, self.num_heads, self.qk_head_dim)
 
         # can be W_Q or W_UQ depending q_lora_rank, the former if
         # q_lora_rank is None, the latter otherwise. From the Attention backend
         # perspective though we call these both W_Q and rely on the layer
         # to pass in the correct matrix
-        W_Q = q_proj[..., :self.qk_nope_head_dim]
-        self.W_QR = q_proj[..., self.qk_nope_head_dim:]\
+        W_Q = q_proj_weight[..., :self.qk_nope_head_dim]
+        self.W_QR = q_proj_weight[..., self.qk_nope_head_dim:]\
             .flatten(start_dim=1).contiguous()
 
+        # W_QR is small so for simplicity we dont bother requantizing it
+        self.W_QR = self.W_QR.to(act_dtype)
+
         if envs.VLLM_MLA_PERFORM_MATRIX_ABSORPTION:
+            requantization_enabled = not envs.VLLM_MLA_DISABLE_REQUANTIZATION
+            if is_fp8(weight_dtype) and requantization_enabled:
+                # This assumes it wise to requantize using the same group shapes
+                # (i.e. strategy, per-tensor, per-channel, block etc.) that the
+                # weights were originally quantized
+                requant_input_group_shape, requant_weight_group_shape = \
+                    get_scale_group_shapes_for_fp8(self.q_proj)
+                assert (requant_input_group_shape, requant_weight_group_shape)\
+                    == get_scale_group_shapes_for_fp8(self.kv_b_proj)
+                assert (requant_input_group_shape, requant_weight_group_shape)\
+                    == get_scale_group_shapes_for_fp8(self.o_proj)
+                self.reqaunt_input_group_shape = requant_input_group_shape
+                self.reqaunt_weight_group_shape = requant_weight_group_shape
+
             #
             # Perform matrix-absorption following
             #     https://github.com/flashinfer-ai/flashinfer/pull/551
@@ -223,25 +352,44 @@ class MLACommonImpl(MLAAttentionImpl[T], Generic[T]):
             # latter otherwise
             # basically if q_lora_rank is none we are absorbing into q_proj
             # instead of UQ
-            self.W_Q_UK = torch.einsum("qnd,lnd -> qnl", W_Q, W_UK)\
+            W_Q_UK = torch.einsum("qnd,lnd -> qnl", W_Q, W_UK)\
                 .flatten(start_dim=1).contiguous()
 
-            W_O = self.o_proj.weight\
+            if is_fp8(weight_dtype) and requantization_enabled:
+                W_Q_UK, W_Q_UK_scales = scaled_quantize(
+                    W_Q_UK,
+                    self.reqaunt_weight_group_shape,
+                    quant_dtype=current_platform_fp8_dtype)
+                # For FP8 save the transpose so we can use
+                # `apply_w8a8_block_fp8_linear` directly
+                self.W_Q_UK = W_Q_UK.T.contiguous()
+                self.W_Q_UK_scales = W_Q_UK_scales.T.contiguous()
+            else:
+                self.W_Q_UK = W_Q_UK.to(act_dtype)
+
+            W_O = get_and_maybe_dequant_weights(self.o_proj)\
                 .view(-1, self.num_heads, self.v_head_dim)
-            self.W_UV_O = torch.einsum("lnd,hnd -> nlh", W_UV, W_O)\
+            W_UV_O = torch.einsum("lnd,hnd -> nlh", W_UV, W_O)\
                 .flatten(start_dim=0, end_dim=1).contiguous()
 
-            tp_size = get_tensor_model_parallel_world_size()
-            self.o_proj_absorbed = RowParallelLinear(
-                self.W_UV_O.shape[0] * tp_size,
-                self.W_UV_O.shape[1],
-                bias=False,
-                # TODO(lucas) figure out how to properly forward quant_method
-                #quant_config=self.o_proj.quant_method,
-            )
-
-            self.o_proj_absorbed.weight = torch.nn.Parameter(self.W_UV_O.T)
+            if is_fp8(weight_dtype) and requantization_enabled:
+                W_UV_O, W_UV_O_scales = scaled_quantize(
+                    W_UV_O,
+                    self.reqaunt_weight_group_shape,
+                    quant_dtype=current_platform_fp8_dtype)
+                # For FP8 save the transpose so we can use
+                # `apply_w8a8_block_fp8_linear` directly
+                self.W_UV_O = W_UV_O.T.contiguous()
+                self.W_UV_O_scales = W_UV_O_scales.T.contiguous()
+            else:
+                self.W_UV_O = W_UV_O.to(act_dtype)
+
+            self.tp_size = get_tensor_model_parallel_world_size()
         else:
+            if is_fp8(weight_dtype):
+                raise NotImplementedError(
+                    "Currently fp8 requires matrix absorption")
+
             self.W_UV = W_UV
             self.W_UK = W_UK
             self.W_Q = W_Q.flatten(start_dim=1)

vllm/attention/backends/triton_mla.py

@@ -57,14 +57,12 @@ class TritonMLABackend(AttentionBackend):
 
     @staticmethod
     def get_kv_cache_shape(
-            num_blocks: int,
-            block_size: int,
-            num_kv_heads: int,  # assumed to be 1 for MLA
-            kv_lora_rank: int,  # passed via head_size
+        num_blocks: int,
+        block_size: int,
+        num_kv_heads: int,  # assumed to be 1 for MLA
+        head_size: int,
     ) -> Tuple[int, ...]:
-        # TODO(lucas): remove hardcoding k_pe size as 1/8th of kv_lora_rank
-        k_pe_size = kv_lora_rank // 8
-        return (num_blocks, block_size, kv_lora_rank + k_pe_size)
+        return (num_blocks, block_size, head_size)
 
     @staticmethod
     def swap_blocks(
@@ -83,7 +81,7 @@ class TritonMLABackend(AttentionBackend):
 
     @staticmethod
     def get_supported_head_sizes() -> List[int]:
-        return [512]
+        return [576]
 
 
 class TritonMLAState(AttentionState):
@@ -624,8 +622,6 @@ class TritonMLAMetadataBuilder(AttentionMetadataBuilder[TritonMLAMetadata]):
             self.multimodal_placeholder_maps.items()
         }
 
-        num_kv_splits = 8
-
         return TritonMLAMetadata(
             num_prefills=self.num_prefills,
             slot_mapping=slot_mapping_tensor,
@@ -645,7 +641,7 @@ class TritonMLAMetadataBuilder(AttentionMetadataBuilder[TritonMLAMetadata]):
             context_lens_tensor=context_lens_tensor,
             block_tables=block_tables,
             use_cuda_graph=use_captured_graph,
-            num_kv_splits=num_kv_splits,
+            num_kv_splits=4,  # TODO(lucas) add heuristic
             head_dim=self.runner.model_config.get_head_size(),
         )
 

vllm/attention/layer.py

@@ -200,9 +200,9 @@ class Attention(nn.Module):
         s += f", backend={self.impl.__class__.__name__}"
         return s
 
-    def process_weights_after_loading(self):
+    def process_weights_after_loading(self, act_dtype: torch.dtype):
         if hasattr(self.impl, "process_weights_after_loading"):
-            self.impl.process_weights_after_loading()
+            self.impl.process_weights_after_loading(act_dtype)
 
 
 class MultiHeadAttention(nn.Module):

vllm/config.py

@@ -739,18 +739,19 @@ class ModelConfig:
     @property
     def is_deepseek_mla(self) -> bool:
         # TODO add deepseek_v3
-        return hasattr(self.hf_text_config,
-                       "model_type") and (self.hf_text_config.model_type
-                                          in ('deepseek_v2'))
+        return (hasattr(self.hf_text_config, "model_type")) \
+                and (self.hf_text_config.model_type in \
+                    ('deepseek_v2', 'deepseek_v3'))\
+                and (self.hf_text_config.kv_lora_rank is not None)
 
     def get_head_size(self) -> int:
         # TODO remove hard code
         if self.is_deepseek_mla:
+            qk_rope_head_dim = getattr(self.hf_text_config, "qk_rope_head_dim",
+                                       0)
             if self.use_mla:
-                return self.hf_text_config.kv_lora_rank
+                return self.hf_text_config.kv_lora_rank + qk_rope_head_dim
             else:
-                qk_rope_head_dim = getattr(self.hf_text_config,
-                                           "qk_rope_head_dim", 0)
                 qk_nope_head_dim = getattr(self.hf_text_config,
                                            "qk_nope_head_dim", 0)
                 if qk_rope_head_dim and qk_nope_head_dim:
@@ -969,6 +970,32 @@ class ModelConfig:
 
     @property
     def use_mla(self) -> bool:
+        if self.quantization is not None and self.quantization not in [\
+            "fp8", "compressed-tensors"]:
+            logger.warning(
+                "MLA is not supported with %s quantization. "
+                "Disabling MLA.", self.quantization)
+            return False
+
+        # If using a "compressed-tensors" checkpoint, check that all groups
+        # have fp8 for both weights and activations.
+        if self.quantization == "compressed-tensors":
+            quant_config = self._parse_quant_hf_config()
+            for group_name, cfg in quant_config.get("config_groups",
+                                                    ("", {})).items():
+                act_cfg = cfg.get("input_activations", {})
+                act_type = None if act_cfg is None else act_cfg.get("type", "")
+                w_cfg = cfg.get("weights", {})
+                w_type = None if w_cfg is None else w_cfg.get("type", "")
+                if act_type != "fp8" or w_type != "fp8":
+                    logger.warning(
+                        "compressed-tensors MLA support requires fp8 "
+                        "activations and weights in group '%s', but got "
+                        "activations type '%s' and weights type '%s'.\n "
+                        "Full config: %s", group_name, act_type, w_type,
+                        quant_config)
+                    return False
+
         use_mla = (self.is_deepseek_mla and not envs.VLLM_MLA_DISABLE)
         return use_mla
 

vllm/envs.py

@@ -79,6 +79,7 @@ if TYPE_CHECKING:
     VLLM_V1_OUTPUT_PROC_CHUNK_SIZE: int = 128
     VLLM_MLA_DISABLE: bool = False
     VLLM_MLA_PERFORM_MATRIX_ABSORPTION: bool = True
+    VLLM_MLA_DISABLE_REQUANTIZATION: bool = False
 
 
 def get_default_cache_root():
@@ -519,7 +520,16 @@ environment_variables: Dict[str, Callable[[], Any]] = {
     # storing more weights, W_Q_UK and W_UV_O, so can increase memory usage,
     # the is enabled by default
     "VLLM_MLA_PERFORM_MATRIX_ABSORPTION":
-    lambda: bool(int(os.getenv("VLLM_MLA_PERFORM_MATRIX_ABSORPTION", "1")))
+    lambda: bool(int(os.getenv("VLLM_MLA_PERFORM_MATRIX_ABSORPTION", "1"))),
+
+    # When running MLA with matrix-absorption enabled and fp8 quantized weights
+    # we perform the matrix-absorption in float32 precision, after the matrices
+    # are absorbed we requantize the weights back to fp8, this flag can be used
+    # to disable the requantization step, and instead convert the absorbed
+    # matrices to match the activation type. This can lead to higher memory and
+    # compute usage but better preserves the accuracy of the original model.
+    "VLLM_MLA_DISABLE_REQUANTIZATION":
+    lambda: bool(int(os.getenv("VLLM_MLA_DISABLE_REQUANTIZATION", "0")))
 }
 
 # end-env-vars-definition

vllm/model_executor/layers/quantization/utils/fp8_utils.py

@@ -2,7 +2,7 @@
 import functools
 import json
 import os
-from typing import Any, Dict, List, Optional, Tuple
+from typing import Any, Dict, List, Optional, Tuple, Union
 
 import torch
 import triton
@@ -10,10 +10,24 @@ import triton.language as tl
 
 from vllm import _custom_ops as ops
 from vllm.logger import init_logger
+from vllm.model_executor.layers.quantization.utils.quant_utils import (
+    _normalize_quant_group_shape, scaled_dequantize)
+from vllm.model_executor.layers.quantization.utils.w8a8_utils import (
+    apply_fp8_linear)
 from vllm.platforms import current_platform
 
 logger = init_logger(__name__)
 
+current_platform_fp8_dtype = (torch.float8_e4m3fnuz
+                              if current_platform.is_rocm() else
+                              torch.float8_e4m3fn)
+
+
+def is_fp8(x: Union[torch.dtype, torch.Tensor]) -> bool:
+    if isinstance(x, torch.Tensor):
+        x = x.dtype
+    return x == torch.float8_e4m3fn or x == torch.float8_e4m3fnuz
+
 
 def apply_w8a8_block_fp8_linear(
     input: torch.Tensor,
@@ -55,6 +69,42 @@ def apply_w8a8_block_fp8_linear(
     return output.to(dtype=input.dtype).view(*output_shape)
 
 
+# Unify the interface between `apply_w8a8_block_fp8_linear` and
+# `apply_fp8_linear`
+# NOTE(lucas): this is quite messy, we should think through this more formally
+def apply_fp8_linear_generic(
+        input: torch.Tensor,
+        weight: torch.Tensor,
+        weight_scale: torch.Tensor,
+        input_group_shape: Tuple[int, int],
+        weight_group_shape: Tuple[int, int],
+        input_scale: Optional[torch.Tensor] = None,  # static scale if one
+) -> torch.Tensor:
+    # View input as 2D matrix for fp8 methods
+    input = input.view(-1, input.shape[-1])
+
+    weight_group_shape = _normalize_quant_group_shape(\
+        weight, weight_group_shape)
+    input_group_shape = _normalize_quant_group_shape(input, input_group_shape)
+
+    def is_dim_blocked(dim, shape, group_shape):
+        return group_shape < shape[dim] and group_shape > 1
+
+    if is_dim_blocked(0, weight.shape, weight_group_shape[0])\
+     and is_dim_blocked(1, weight.shape, weight_group_shape[1]) and\
+     input_group_shape == (1, weight_group_shape[1]):
+        return apply_w8a8_block_fp8_linear(input, weight,
+                                           list(weight_group_shape),
+                                           weight_scale)
+    else:
+        # Despite having linear in the it doesn't conform to
+        # `torch.nn.functional.linear` which is defined as `input @ weight.T`
+        # so we explicitly transpose the weight matrix here
+        return apply_fp8_linear(input, weight.T, weight_scale.T,
+                         use_per_token_if_dynamic=\
+                             (input_group_shape == (1, input.shape[1])))
+
+
 def input_to_float8(
         x: torch.Tensor,
         dtype: Optional[torch.dtype] = None
@@ -75,7 +125,6 @@ def input_to_float8(
 def block_quant_to_tensor_quant(
     x_q_block: torch.Tensor,
     x_s: torch.Tensor,
-    block_size: List[int],
 ) -> Tuple[torch.Tensor, torch.Tensor]:
     """This function converts block-wise quantization to tensor-wise
     quantization. The inputs are block-wise quantization tensor `x_q_block`,
@@ -83,26 +132,7 @@ def block_quant_to_tensor_quant(
     The outputs are tensor-wise quantization tensor and tensor-wise
     quantization scale. Note only float8 is supported for now.
     """
-    block_n, block_k = block_size[0], block_size[1]
-    n, k = x_q_block.shape
-    n_tiles = (n + block_n - 1) // block_n
-    k_tiles = (k + block_k - 1) // block_k
-    assert n_tiles == x_s.shape[0]
-    assert k_tiles == x_s.shape[1]
-
-    x_dq_block = x_q_block.to(torch.float32)
-
-    x_dq_block_tiles = [[
-        x_dq_block[
-            j * block_n:min((j + 1) * block_n, n),
-            i * block_k:min((i + 1) * block_k, k),
-        ] for i in range(k_tiles)
-    ] for j in range(n_tiles)]
-
-    for i in range(k_tiles):
-        for j in range(n_tiles):
-            x_dq_block_tiles[j][i][:, :] = x_dq_block_tiles[j][i] * x_s[j][i]
-
+    x_dq_block = scaled_dequantize(x_q_block, x_s)
     x_q_tensor, scale = input_to_float8(x_dq_block, dtype=x_q_block.dtype)
     return x_q_tensor, scale
 

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

 """This file is used for /tests and /benchmarks"""
-from typing import List, Optional
+from typing import List, Optional, Tuple
 
 import numpy
 import torch
@@ -20,6 +20,120 @@ FUSED_LAYER_NAME_MAPPING = {
 }
 
 
+# Normalize the group_shape to the full extent for any dims that are -1
+def _normalize_quant_group_shape(x: torch.Tensor, group_shape: Tuple[int,
+                                                                     int]):
+    # -1 means full extent
+    return (group_shape[0] if group_shape[0] > 0 else x.shape[-2],
+            group_shape[1] if group_shape[1] > 0 else x.shape[-1])
+
+
+# Useful when treating N-dimensional group scaling as extended numpy-style
+# broadcasting in numpy simply stretches dimensions with an extent of 1 to match
+# the target shape by repeating the data along that dimension (broadcasting)
+# , we extend these semantics to say if the extent of a dimension in the
+# source shape is not 1 and does not match the target shape we repeat each
+# element along that dimension src_shape[dim] // target_shape[dim] times
+# example if we have:
+#       a = [[1, 2], and target_shape = (2, 4)
+#            [3, 4]]
+# then we would expand a to:
+#       a = [[1, 1, 2, 2],
+#            [3, 3, 4, 4]]
+# NOTE this function this function does not explicitly broadcast dimensions
+# with an extent of 1, since this can be done implicitly by pytorch
+def group_broadcast(t, shape):
+    for i, s in enumerate(shape):
+        if t.shape[i] != s and t.shape[i] != 1:
+            assert s % t.shape[i] == 0
+            t = t.unsqueeze(i + 1)\
+                .expand(*t.shape[:i+1], s // t.shape[i], *t.shape[i+1:])\
+                .flatten(i, i + 1)
+    return t
+
+
+# Quantize assuming once scale per group of elements with shape group_shape,
+# example group shapes:
+#  * (-1, -1)   for per-tensor quantization
+#  * (1, -1)    for per-row quantization
+#  * (-1, 1)    for per-column quantization
+#  * (128, 128) for 128x128 deepseek style block quantization
+#  * (1, 128)   for deepseek style activation quantization
+#               (i.e. per-token-per-group)
+def scaled_quantize(
+    x: torch.Tensor,
+    group_shape: Tuple[int, int],
+    quant_dtype: torch.dtype,
+) -> Tuple[torch.Tensor, torch.Tensor]:
+    group_shape = _normalize_quant_group_shape(x, group_shape)
+    assert quant_dtype.is_floating_point, \
+        "currently `scaled_quantize` only supports floating point dtypes " \
+        "but could be extended to support other dtypes"
+
+    finfo = torch.finfo(quant_dtype)
+
+    # Reshape (M, N) into (BLK_M, BLOCK_SIZE_M, BLK_N, BLOCK_SIZE_N)
+    assert x.ndim == 2
+    assert x.shape[0] % group_shape[0] == 0 and x.shape[1] % group_shape[1] == 0
+    blk_m, blk_n = x.shape[0] // group_shape[0], x.shape[1] // group_shape[1]
+    x_blkd = x.reshape(blk_m, group_shape[0], blk_n, group_shape[1])
+
+    # Permute to (BLK_M, BLK_N, BLOCK_SIZE_M, BLOCK_SIZE_N)
+    x_blkd_permd = x_blkd.permute(0, 2, 1, 3)
+    # Flatten to (BLK_M, BLK_N, BLOCK_SIZE_M * BLOCK_SIZE_N)
+    x_blkd_permd = x_blkd_permd.flatten(start_dim=2)
+
+    # Compute scales
+    min_val, max_val = x_blkd_permd.aminmax(dim=-1)
+    amax = torch.maximum(min_val.abs(), max_val.abs()).clamp(min=1e-12)
+    scale = finfo.max / amax
+
+    # Apply scale and convert form:
+    # (BLK_M, BLK_N, BLOCK_SIZE_M * BLOCK_SIZE_N) to (M, N)
+    x_scl_sat = (x_blkd_permd * scale.unsqueeze(-1))\
+        .clamp(min=finfo.min, max=finfo.max)\
+        .reshape(blk_m, blk_n, group_shape[0], group_shape[1])\
+        .permute(0, 2, 1, 3)\
+        .reshape(x.shape)
+
+    return x_scl_sat.to(quant_dtype).contiguous(), scale.float().reciprocal()
+
+
+# inverses `scaled_quantize`
+def scaled_dequantize(
+    x_q: torch.Tensor,
+    x_s: torch.Tensor,
+    group_shape: Optional[Tuple[int, int]] = None,
+    out_dtype: torch.dtype = torch.float32,
+) -> Tuple[torch.Tensor, torch.Tensor]:
+    if group_shape is not None:
+        group_shape = _normalize_quant_group_shape(x_q, group_shape)
+
+    if x_s.ndim == 0:  # scalar
+        x_s = x_s.unsqueeze(-1).unsqueeze(-1)  # convert to (1, 1) tensor
+    if x_s.ndim == 1:
+        if group_shape is None:
+            raise AssertionError(
+                "if x_s is 1D tensor, group_shape must be provided otherwise "
+                "its ambiguous which dimension to broadcast x_s to")
+        # unsqueeze the scales for the dimension where we want to broadcast
+        # across the full extent
+        if group_shape[0] == x_q.shape[-2]:
+            x_s = x_s.unsqueeze(-2)
+        elif group_shape[1] == x_q.shape[-1]:
+            x_s = x_s.unsqueeze(-1)
+        else:
+            raise AssertionError(
+                "if x_s is a vector we should be broadcasting it to the full "
+                "extent of one of the dimensions")
+
+    if group_shape is not None:
+        assert x_s.shape[-1] == x_q.shape[-1] // group_shape[1]
+        assert x_s.shape[-2] == x_q.shape[-2] // group_shape[0]
+    x_s = group_broadcast(x_s.to(torch.float32), x_q.shape)
+    return (x_q.to(torch.float32) * x_s).to(out_dtype)
+
+
 def pack_quantized_values_into_int32(w_q: torch.Tensor,
                                      wtype: ScalarType,
                                      packed_dim: int = 0):

vllm/model_executor/model_loader/loader.py

@@ -398,11 +398,13 @@ class DefaultModelLoader(BaseModelLoader):
                     # parameters onto device for processing and back off after.
                     with device_loading_context(module, target_device):
                         quant_method.process_weights_after_loading(module)
-                elif isinstance(module, Attention) and \
+                if isinstance(module, Attention) and \
                     hasattr(module, "process_weights_after_loading"):
                     # When attention modules need to process weights after
                     # currently only used by MLA
-                    module.process_weights_after_loading()
+                    # TODO(lucas): see if there is a way to unify the signatures
+                    # of process_weights_after_loading
+                    module.process_weights_after_loading(model_config.dtype)
         return model.eval()
 
 
@@ -439,6 +441,11 @@ class DummyModelLoader(BaseModelLoader):
                     with device_loading_context(
                             module, torch.device(device_config.device)):
                         quant_method.process_weights_after_loading(module)
+                if isinstance(module, Attention) and \
+                    hasattr(module, "process_weights_after_loading"):
+                    # When attention modules need to process weights after
+                    # currently only used by MLA
+                    module.process_weights_after_loading(model_config.dtype)
         return model.eval()
 
 
@@ -633,6 +640,12 @@ class ShardedStateLoader(BaseModelLoader):
                     quant_method = getattr(module, "quant_method", None)
                     if quant_method is not None:
                         quant_method.process_weights_after_loading(module)
+                    if isinstance(module, Attention) and \
+                        hasattr(module, "process_weights_after_loading"):
+                        # When attention modules need to process weights after
+                        # currently only used by MLA
+                        module.process_weights_after_loading(
+                            model_config.dtype)
             rank = get_tensor_model_parallel_rank()
             pattern = os.path.join(
                 local_model_path,
@@ -1272,7 +1285,7 @@ class GGUFModelLoader(BaseModelLoader):
 
 class RunaiModelStreamerLoader(BaseModelLoader):
     """
-        Model loader that can load safetensors 
+        Model loader that can load safetensors
         files from local FS or S3 bucket.
     """
 
@@ -1369,6 +1382,11 @@ class RunaiModelStreamerLoader(BaseModelLoader):
                 if quant_method is not None:
                     with device_loading_context(module, target_device):
                         quant_method.process_weights_after_loading(module)
+                if isinstance(module, Attention) and \
+                    hasattr(module, "process_weights_after_loading"):
+                    # When attention modules need to process weights after
+                    # currently only used by MLA
+                    module.process_weights_after_loading(model_config.dtype)
         return model.eval()
 
 

vllm/model_executor/models/deepseek_v3.py

@@ -27,7 +27,7 @@ from torch import nn
 from transformers import PretrainedConfig
 
 from vllm.attention import Attention, AttentionMetadata
-from vllm.config import CacheConfig, VllmConfig
+from vllm.config import CacheConfig, ModelConfig, VllmConfig
 from vllm.distributed import (get_pp_group,
                               get_tensor_model_parallel_world_size,
                               tensor_model_parallel_all_reduce)
@@ -333,12 +333,156 @@ class DeepseekV3Attention(nn.Module):
         return output
 
 
+class DeepseekV3MLAAttention(nn.Module):
+    """
+    Main reference: DeepseekV2 paper, and FlashInfer Implementation
+    (https://arxiv.org/abs/2405.04434 and https://github.com/flashinfer-ai/flashinfer/pull/551).
+    
+    For more info see MLACommonImpl in: vllm/attention/backends/mla/utils.py
+    """
+
+    def __init__(
+        self,
+        config: PretrainedConfig,
+        hidden_size: int,
+        num_heads: int,
+        qk_nope_head_dim: int,
+        qk_rope_head_dim: int,
+        v_head_dim: int,
+        q_lora_rank: Optional[int],
+        kv_lora_rank: int,
+        rope_theta: float = 10000,
+        rope_scaling: Optional[Dict[str, Any]] = None,
+        max_position_embeddings: int = 8192,
+        cache_config: Optional[CacheConfig] = None,
+        quant_config: Optional[QuantizationConfig] = None,
+        prefix: str = "",
+    ) -> None:
+        super().__init__()
+        self.hidden_size = hidden_size
+        self.qk_nope_head_dim = qk_nope_head_dim
+        self.qk_rope_head_dim = qk_rope_head_dim
+        self.qk_head_dim = qk_nope_head_dim + qk_rope_head_dim
+        self.v_head_dim = v_head_dim
+
+        self.q_lora_rank = q_lora_rank
+        self.kv_lora_rank = kv_lora_rank
+
+        self.num_heads = num_heads
+        tp_size = get_tensor_model_parallel_world_size()
+        assert num_heads % tp_size == 0
+        self.num_local_heads = num_heads // tp_size
+
+        self.scaling = self.qk_head_dim**-0.5
+        self.rope_theta = rope_theta
+        self.max_position_embeddings = max_position_embeddings
+
+        if self.q_lora_rank is not None:
+            self.q_a_proj = ReplicatedLinear(self.hidden_size,
+                                             self.q_lora_rank,
+                                             bias=False,
+                                             quant_config=quant_config,
+                                             prefix=f"{prefix}.q_a_proj")
+            self.q_a_layernorm = RMSNorm(self.q_lora_rank,
+                                         eps=config.rms_norm_eps)
+            self.q_b_proj = ColumnParallelLinear(q_lora_rank,
+                                                 self.num_heads *
+                                                 self.qk_head_dim,
+                                                 bias=False,
+                                                 quant_config=quant_config,
+                                                 prefix=f"{prefix}.q_b_proj")
+        else:
+            self.q_proj = ColumnParallelLinear(self.hidden_size,
+                                               self.num_heads *
+                                               self.qk_head_dim,
+                                               bias=False,
+                                               quant_config=quant_config,
+                                               prefix=f"{prefix}.q_proj")
+
+        self.kv_a_proj_with_mqa = ReplicatedLinear(
+            self.hidden_size,
+            self.kv_lora_rank + self.qk_rope_head_dim,
+            bias=False,
+            quant_config=quant_config,
+            prefix=f"{prefix}.kv_a_proj_with_mqa")
+        self.kv_a_layernorm = RMSNorm(self.kv_lora_rank,
+                                      eps=config.rms_norm_eps)
+        self.kv_b_proj = ColumnParallelLinear(
+            self.kv_lora_rank,
+            self.num_heads * (self.qk_nope_head_dim + self.v_head_dim),
+            bias=False,
+            quant_config=quant_config,
+            prefix=f"{prefix}.kv_b_proj")
+        self.o_proj = RowParallelLinear(self.num_heads * self.v_head_dim,
+                                        self.hidden_size,
+                                        bias=False,
+                                        quant_config=quant_config,
+                                        prefix=f"{prefix}.o_proj")
+
+        rope_scaling["rope_type"] = 'deepseek_yarn'
+        self.rotary_emb = get_rope(qk_rope_head_dim,
+                                   rotary_dim=qk_rope_head_dim,
+                                   max_position=max_position_embeddings,
+                                   base=rope_theta,
+                                   rope_scaling=rope_scaling,
+                                   is_neox_style=False)
+        if rope_scaling:
+            mscale_all_dim = rope_scaling.get("mscale_all_dim", False)
+            scaling_factor = rope_scaling["factor"]
+            mscale = yarn_get_mscale(scaling_factor, float(mscale_all_dim))
+            self.scaling = self.scaling * mscale * mscale
+
+        self.mla_attn = Attention(
+            num_heads=self.num_local_heads,
+            head_size=self.kv_lora_rank,
+            scale=self.scaling,
+            num_kv_heads=1,
+            cache_config=cache_config,
+            quant_config=quant_config,
+            prefix=f"{prefix}.attn",
+            use_mla=True,
+            # MLA Args
+            q_lora_rank=self.q_lora_rank,
+            kv_lora_rank=self.kv_lora_rank,
+            qk_nope_head_dim=self.qk_nope_head_dim,
+            qk_rope_head_dim=self.qk_rope_head_dim,
+            qk_head_dim=self.qk_head_dim,
+            v_head_dim=self.v_head_dim,
+            rotary_emb=self.rotary_emb,
+            q_proj=self.q_proj if self.q_lora_rank is None else self.q_b_proj,
+            kv_b_proj=self.kv_b_proj,
+            o_proj=self.o_proj,
+        )
+
+        self.prefix = prefix
+        self.debug_layer_idx = int(self.prefix.split(".")[-2])
+
+    def forward(
+        self,
+        positions: torch.Tensor,
+        hidden_states: torch.Tensor,
+        kv_cache: torch.Tensor,
+        attn_metadata: AttentionMetadata,
+    ) -> torch.Tensor:
+        if self.q_lora_rank is not None:
+            ckq = self.q_a_proj(hidden_states)[0]
+            hidden_states_or_q_c = self.q_a_layernorm(ckq)
+        else:
+            hidden_states_or_q_c = hidden_states
+        kv_c, k_pe = self.kv_a_proj_with_mqa(hidden_states)[0].split(
+            [self.kv_lora_rank, self.qk_rope_head_dim], dim=-1)
+        kv_c_normed = self.kv_a_layernorm(kv_c.contiguous())
+        return self.mla_attn(hidden_states_or_q_c, kv_c_normed, k_pe, kv_cache,
+                             attn_metadata)
+
+
 class DeepseekV3DecoderLayer(nn.Module):
 
     def __init__(
         self,
         config: PretrainedConfig,
         prefix: str,
+        model_config: ModelConfig,
         cache_config: Optional[CacheConfig] = None,
         quant_config: Optional[QuantizationConfig] = None,
     ) -> None:
@@ -351,7 +495,11 @@ class DeepseekV3DecoderLayer(nn.Module):
         # DecoderLayers are created with `make_layers` which passes the prefix
         # with the layer's index.
         layer_idx = int(prefix.split(sep='.')[-1])
-        self.self_attn = DeepseekV3Attention(
+        if model_config.use_mla:
+            attn_cls = DeepseekV3MLAAttention
+        else:
+            attn_cls = DeepseekV3Attention
+        self.self_attn = attn_cls(
             config=config,
             hidden_size=self.hidden_size,
             num_heads=config.num_attention_heads,
@@ -428,6 +576,7 @@ class DeepseekV3Model(nn.Module):
         super().__init__()
 
         config = vllm_config.model_config.hf_config
+        model_config = vllm_config.model_config
         cache_config = vllm_config.cache_config
         quant_config = vllm_config.quant_config
 
@@ -447,6 +596,7 @@ class DeepseekV3Model(nn.Module):
             lambda prefix: DeepseekV3DecoderLayer(
                 config,
                 prefix,
+                model_config=model_config,
                 cache_config=cache_config,
                 quant_config=quant_config,
             ),

vllm/worker/cache_engine.py

@@ -110,7 +110,9 @@ class CacheEngine:
             parallel_config, LayerBlockType.attention)
 
         key_cache_block = cache_config.block_size * num_heads * head_size
-        value_cache_block = key_cache_block
+        # For MLA there is no value cache, since the latent vector
+        # is joint keys and values.
+        value_cache_block = key_cache_block if not model_config.use_mla else 0
         total = num_attention_layers * (key_cache_block + value_cache_block)
         if cache_config.cache_dtype == "auto":
             dtype = model_config.dtype