From cb295bf59663cd3577389315636772f4060bd1f5 Mon Sep 17 00:00:00 2001
From: Alexey Kopytko <alexey@kopytko.com>
Date: Mon, 6 Jul 2026 23:26:50 +0900
Subject: [PATCH] CUDA: extend K-type validation to V-types for flash attention
 (#24403)

* CUDA: extend K-type validation to V-types for flash attention

* reorder
---
 ggml/src/ggml-cuda/fattn.cu | 38 +++++++++++++++++++++----------------
 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/ggml/src/ggml-cuda/fattn.cu b/ggml/src/ggml-cuda/fattn.cu
index c3039211c1..00ffacf299 100644
--- a/ggml/src/ggml-cuda/fattn.cu
+++ b/ggml/src/ggml-cuda/fattn.cu
@@ -337,6 +337,26 @@ enum best_fattn_kernel {
     BEST_FATTN_KERNEL_MMA_F16  = 400,
 };
 
+static bool ggml_cuda_fattn_kv_type_supported(ggml_type type) {
+    switch (type) {
+        case GGML_TYPE_F32:
+        case GGML_TYPE_F16:
+            return true;
+        case GGML_TYPE_Q4_1:
+        case GGML_TYPE_Q5_0:
+        case GGML_TYPE_Q5_1:
+#ifndef GGML_CUDA_FA_ALL_QUANTS
+            return false;
+#endif // GGML_CUDA_FA_ALL_QUANTS
+        case GGML_TYPE_Q4_0:
+        case GGML_TYPE_Q8_0:
+        case GGML_TYPE_BF16:
+            return true;
+        default:
+            return false;
+    }
+}
+
 static best_fattn_kernel ggml_cuda_get_best_fattn_kernel(const int device, const ggml_tensor * dst) {
 #ifndef FLASH_ATTN_AVAILABLE
     GGML_UNUSED(device); GGML_UNUSED(dst);
@@ -427,22 +447,8 @@ static best_fattn_kernel ggml_cuda_get_best_fattn_kernel(const int device, const
     }
 #endif // GGML_CUDA_FA_ALL_QUANTS
 
-    switch (K->type) {
-        case GGML_TYPE_F32:
-        case GGML_TYPE_F16:
-            break;
-        case GGML_TYPE_Q4_1:
-        case GGML_TYPE_Q5_0:
-        case GGML_TYPE_Q5_1:
-#ifndef GGML_CUDA_FA_ALL_QUANTS
-            return BEST_FATTN_KERNEL_NONE;
-#endif // GGML_CUDA_FA_ALL_QUANTS
-        case GGML_TYPE_Q4_0:
-        case GGML_TYPE_Q8_0:
-        case GGML_TYPE_BF16:
-            break;
-        default:
-            return BEST_FATTN_KERNEL_NONE;
+    if (!ggml_cuda_fattn_kv_type_supported(K->type) || !ggml_cuda_fattn_kv_type_supported(V->type)) {
+        return BEST_FATTN_KERNEL_NONE;
     }
 
     if (mask && mask->ne[2] != 1) {