[Misc] Add `float16` to `CacheDType` (#37199)

Signed-off-by: Matthew Bonanni <mbonanni@redhat.com>

docs/design/attention_backends.md

@@ -164,18 +164,18 @@ Priority is **1 = highest** (tried first).
 | Backend | Version | Dtypes | KV Dtypes | Block Sizes | Head Sizes | Sink | MM Prefix | DCP | Attention Types | Compute Cap. |
 | ------- | ------- | ------ | --------- | ----------- | ---------- | ---- | --------- | --- | --------------- | ------------ |
 | `CPU_ATTN` | | fp16, bf16, fp32 | `auto` | Any | 32, 64, 80, 96, 112, 128, 160, 192, 224, 256 | ❌ | ❌ | ❌ | All | N/A |
-| `FLASHINFER` | Native† | fp16, bf16 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | 16, 32, 64 | 64, 128, 256 | ❌ | ❌ | ✅ | Decoder | 7.x-9.x |
-| `FLASHINFER` | TRTLLM† | fp16, bf16 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | 16, 32, 64 | 64, 128, 256 | ✅ | ❌ | ✅ | Decoder | 10.x |
-| `FLASH_ATTN` | FA2* | fp16, bf16 | `auto`, `bfloat16` | %16 | Any | ❌ | ❌ | ✅ | All | ≥8.0 |
-| `FLASH_ATTN` | FA3* | fp16, bf16 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | %16 | Any | ✅ | ❌ | ✅ | All | 9.x |
-| `FLASH_ATTN` | FA4* | fp16, bf16 | `auto`, `bfloat16` | %16 | Any | ❌ | ❌ | ✅ | All | ≥10.0 |
+| `FLASHINFER` | Native† | fp16, bf16 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | 16, 32, 64 | 64, 128, 256 | ❌ | ❌ | ✅ | Decoder | 7.x-9.x |
+| `FLASHINFER` | TRTLLM† | fp16, bf16 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | 16, 32, 64 | 64, 128, 256 | ✅ | ❌ | ✅ | Decoder | 10.x |
+| `FLASH_ATTN` | FA2* | fp16, bf16 | `auto`, `float16`, `bfloat16` | %16 | Any | ❌ | ❌ | ✅ | All | ≥8.0 |
+| `FLASH_ATTN` | FA3* | fp16, bf16 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | %16 | Any | ✅ | ❌ | ✅ | All | 9.x |
+| `FLASH_ATTN` | FA4* | fp16, bf16 | `auto`, `float16`, `bfloat16` | %16 | Any | ❌ | ❌ | ✅ | All | ≥10.0 |
 | `FLASH_ATTN_DIFFKV` | | fp16, bf16 | `auto` | Any | Any | ❌ | ❌ | ✅ | Decoder | Any |
-| `FLEX_ATTENTION` | | fp16, bf16, fp32 | `auto`, `bfloat16` | Any | Any | ❌ | ✅ | ❌ | Decoder, Encoder Only | Any |
-| `ROCM_AITER_FA` | | fp16, bf16 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | 16, 32 | 64, 128, 256 | ❌ | ❌ | ❌ | Decoder, Enc-Dec | N/A |
+| `FLEX_ATTENTION` | | fp16, bf16, fp32 | `auto`, `float16`, `bfloat16` | Any | Any | ❌ | ✅ | ❌ | Decoder, Encoder Only | Any |
+| `ROCM_AITER_FA` | | fp16, bf16 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | 16, 32 | 64, 128, 256 | ❌ | ❌ | ❌ | Decoder, Enc-Dec | N/A |
 | `ROCM_AITER_UNIFIED_ATTN` | | fp16, bf16 | `auto` | %16 | Any | ✅ | ✅ | ❌ | All | N/A |
-| `ROCM_ATTN` | | fp16, bf16, fp32 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | %16 | 32, 64, 80, 96, 128, 160, 192, 224, 256 | ✅ | ✅ | ❌ | All | N/A |
-| `TREE_ATTN` | | fp16, bf16 | `auto` | %16 | 32, 64, 96, 128, 160, 192, 224, 256 | ❌ | ❌ | ❌ | Decoder | Any |
-| `TRITON_ATTN` | | fp16, bf16, fp32 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | %16 | Any | ✅ | ✅ | ❌ | All | Any |
+| `ROCM_ATTN` | | fp16, bf16, fp32 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | %16 | 32, 64, 80, 96, 128, 160, 192, 224, 256 | ✅ | ✅ | ❌ | All | N/A |
+| `TREE_ATTN` | | fp16, bf16 | `auto`, `float16`, `bfloat16` | %16 | 32, 64, 96, 128, 160, 192, 224, 256 | ❌ | ❌ | ❌ | Decoder | Any |
+| `TRITON_ATTN` | | fp16, bf16, fp32 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | %16 | Any | ✅ | ✅ | ❌ | All | Any |
 
 > **†** FlashInfer uses TRTLLM attention on Blackwell (SM100), which supports sinks. Disable via `--attention-config.use_trtllm_attention=0`.
 >
@@ -204,14 +204,14 @@ configuration.
 
 | Backend | Dtypes | KV Dtypes | Block Sizes | Head Sizes | Sink | Sparse | MM Prefix | DCP | Attention Types | Compute Cap. |
 | ------- | ------ | --------- | ----------- | ---------- | ---- | ------ | --------- | --- | --------------- | ------------ |
-| `CUTLASS_MLA` | fp16, bf16 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3` | 128 | Any | ❌ | ❌ | ❌ | ✅ | Decoder | 10.x |
-| `FLASHINFER_MLA` | fp16, bf16 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3` | 32, 64 | Any | ❌ | ❌ | ❌ | ❌ | Decoder | 10.x |
-| `FLASHINFER_MLA_SPARSE` | fp16, bf16 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3` | 32, 64 | 576 | ❌ | ✅ | ❌ | ❌ | Decoder | 10.x |
-| `FLASHMLA` | fp16, bf16 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3` | 64 | Any | ❌ | ❌ | ❌ | ✅ | Decoder | 9.x-10.x |
+| `CUTLASS_MLA` | fp16, bf16 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3` | 128 | Any | ❌ | ❌ | ❌ | ✅ | Decoder | 10.x |
+| `FLASHINFER_MLA` | fp16, bf16 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3` | 32, 64 | Any | ❌ | ❌ | ❌ | ❌ | Decoder | 10.x |
+| `FLASHINFER_MLA_SPARSE` | fp16, bf16 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3` | 32, 64 | 576 | ❌ | ✅ | ❌ | ❌ | Decoder | 10.x |
+| `FLASHMLA` | fp16, bf16 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3` | 64 | Any | ❌ | ❌ | ❌ | ✅ | Decoder | 9.x-10.x |
 | `FLASHMLA_SPARSE` | bf16 | `auto`, `bfloat16`, `fp8_ds_mla` | 64 | 576 | ❌ | ✅ | ❌ | ❌ | Decoder | 9.x-10.x |
-| `FLASH_ATTN_MLA` | fp16, bf16 | `auto`, `bfloat16` | %16 | Any | ❌ | ❌ | ❌ | ✅ | Decoder | 9.x |
-| `ROCM_AITER_MLA` | fp16, bf16 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | 1 | Any | ❌ | ❌ | ❌ | ❌ | Decoder | N/A |
-| `ROCM_AITER_MLA_SPARSE` | fp16, bf16 | `auto`, `bfloat16` | 1 | Any | ❌ | ✅ | ❌ | ❌ | Decoder | N/A |
+| `FLASH_ATTN_MLA` | fp16, bf16 | `auto`, `float16`, `bfloat16` | %16 | Any | ❌ | ❌ | ❌ | ✅ | Decoder | 9.x |
+| `ROCM_AITER_MLA` | fp16, bf16 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3`, `fp8_e5m2` | 1 | Any | ❌ | ❌ | ❌ | ❌ | Decoder | N/A |
+| `ROCM_AITER_MLA_SPARSE` | fp16, bf16 | `auto`, `float16`, `bfloat16` | 1 | Any | ❌ | ✅ | ❌ | ❌ | Decoder | N/A |
 | `ROCM_AITER_TRITON_MLA` | fp16, bf16 | `auto` | Any | Any | ❌ | ❌ | ❌ | ❌ | Decoder | N/A |
-| `TRITON_MLA` | fp16, bf16 | `auto`, `bfloat16`, `fp8`, `fp8_e4m3` | %16 | Any | ❌ | ❌ | ❌ | ✅ | Decoder | Any |
-| `XPU_MLA_SPARSE` | fp16, bf16 | `auto`, `bfloat16` | Any | 576 | ❌ | ✅ | ❌ | ❌ | Decoder | Any |
+| `TRITON_MLA` | fp16, bf16 | `auto`, `float16`, `bfloat16`, `fp8`, `fp8_e4m3` | %16 | Any | ❌ | ❌ | ❌ | ✅ | Decoder | Any |
+| `XPU_MLA_SPARSE` | fp16, bf16 | `auto`, `float16`, `bfloat16` | Any | 576 | ❌ | ✅ | ❌ | ❌ | Decoder | Any |

vllm/config/cache.py

@@ -13,6 +13,7 @@ logger = init_logger(__name__)
 
 CacheDType = Literal[
     "auto",
+    "float16",
     "bfloat16",
     "fp8",
     "fp8_e4m3",

vllm/v1/attention/backend.py

@@ -51,7 +51,11 @@ class AttentionBackend(ABC):
     # makes sure the output tensor is allocated inside the cudagraph.
     accept_output_buffer: bool = False
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
-    supported_kv_cache_dtypes: ClassVar[list["CacheDType"]] = ["auto", "bfloat16"]
+    supported_kv_cache_dtypes: ClassVar[list["CacheDType"]] = [
+        "auto",
+        "float16",
+        "bfloat16",
+    ]
 
     # Does attention's forward() include kv cache update?
     forward_includes_kv_cache_update: bool = True

vllm/v1/attention/backends/flash_attn.py

@@ -64,6 +64,11 @@ logger = init_logger(__name__)
 class FlashAttentionBackend(AttentionBackend):
     accept_output_buffer: bool = True
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
+    supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
+        "auto",
+        "float16",
+        "bfloat16",
+    ]
 
     @staticmethod
     def get_supported_kernel_block_sizes() -> list[int | MultipleOf]:
@@ -164,7 +169,7 @@ class FlashAttentionBackend(AttentionBackend):
             return True
         if kv_cache_dtype.startswith("fp8"):
             return flash_attn_supports_fp8()
-        return kv_cache_dtype in ["auto", "bfloat16"]
+        return kv_cache_dtype in ["auto", "float16", "bfloat16"]
 
     @classmethod
     def supports_sink(cls) -> bool:

vllm/v1/attention/backends/flashinfer.py

@@ -291,6 +291,7 @@ class FlashInferBackend(AttentionBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
         "fp8",
         "fp8_e4m3",

vllm/v1/attention/backends/flex_attention.py

@@ -80,7 +80,11 @@ class FlexAttentionBackend(AttentionBackend):
         torch.bfloat16,
         torch.float32,
     ]
-    supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = ["auto", "bfloat16"]
+    supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
+        "auto",
+        "float16",
+        "bfloat16",
+    ]
 
     forward_includes_kv_cache_update: bool = False
 

vllm/v1/attention/backends/mla/cutlass_mla.py

@@ -39,6 +39,7 @@ class CutlassMLABackend(MLACommonBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
         "fp8",
         "fp8_e4m3",

vllm/v1/attention/backends/mla/flashattn_mla.py

@@ -46,6 +46,7 @@ class FlashAttnMLABackend(MLACommonBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
     ]
 

vllm/v1/attention/backends/mla/flashinfer_mla.py

@@ -38,6 +38,7 @@ class FlashInferMLABackend(MLACommonBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
         "fp8",
         "fp8_e4m3",

vllm/v1/attention/backends/mla/flashinfer_mla_sparse.py

@@ -62,6 +62,7 @@ class FlashInferMLASparseBackend(AttentionBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
         "fp8",
         "fp8_e4m3",

vllm/v1/attention/backends/mla/flashmla.py

@@ -49,6 +49,7 @@ class FlashMLABackend(MLACommonBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
         "fp8",
         "fp8_e4m3",

vllm/v1/attention/backends/mla/rocm_aiter_mla.py

@@ -26,6 +26,7 @@ class AiterMLABackend(MLACommonBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
         "fp8",
         "fp8_e4m3",

vllm/v1/attention/backends/mla/rocm_aiter_mla_sparse.py

@@ -82,6 +82,7 @@ class ROCMAiterMLASparseBackend(AttentionBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
     ]
 

vllm/v1/attention/backends/mla/triton_mla.py

@@ -31,6 +31,7 @@ class TritonMLABackend(MLACommonBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
         "fp8",
         "fp8_e4m3",

vllm/v1/attention/backends/mla/xpu_mla_sparse.py

@@ -38,6 +38,7 @@ class XPUMLASparseBackend(AttentionBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
     ]
 

vllm/v1/attention/backends/rocm_aiter_fa.py

@@ -736,6 +736,7 @@ class AiterFlashAttentionBackend(AttentionBackend):
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
         "fp8",
         "fp8_e4m3",

vllm/v1/attention/backends/rocm_attn.py

@@ -166,6 +166,7 @@ class RocmAttentionBackend(AttentionBackend):
     ]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
         "fp8",
         "fp8_e4m3",

vllm/v1/attention/backends/tree_attn.py

@@ -10,6 +10,7 @@ import torch
 
 from vllm import _custom_ops as ops
 from vllm.config import VllmConfig
+from vllm.config.cache import CacheDType
 from vllm.logger import init_logger
 from vllm.v1.attention.backend import (
     AttentionBackend,
@@ -31,6 +32,11 @@ logger = init_logger(__name__)
 class TreeAttentionBackend(AttentionBackend):
     accept_output_buffer: bool = True
     supported_dtypes: ClassVar[list[torch.dtype]] = [torch.float16, torch.bfloat16]
+    supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
+        "auto",
+        "float16",
+        "bfloat16",
+    ]
     forward_includes_kv_cache_update: bool = False
 
     @staticmethod

vllm/v1/attention/backends/triton_attn.py

@@ -263,6 +263,7 @@ class TritonAttentionBackend(AttentionBackend):
     ]
     supported_kv_cache_dtypes: ClassVar[list[CacheDType]] = [
         "auto",
+        "float16",
         "bfloat16",
         "fp8",
         "fp8_e4m3",