[Bugfix] Fix marlin kernel crash on H100 (vllm-project#4218)

This PR addresses the Marlin kernel H100 crash that was reported here: neuralmagic#187.
The reason for the crash was the inline PTX assembly that introduced the async_copy with streaming behavior. The solution is to use the more standard PTX for async_copy (without the fractional L2 policy for "evict_first"). There is no performance difference between standard async_copy PTX and the previous one.

Author: alexm-redhat

csrc/quantization/marlin/marlin_cuda_kernel.cu

@@ -67,20 +67,13 @@ __device__ inline void cp_async4_pred(void *smem_ptr, const void *glob_ptr,
                "r"(smem), "l"(glob_ptr), "n"(BYTES));
 }
 
-// Asynchronous global->shared copy with a cache hint indicating that the values
-// may be evicted immediately; used for quantized weights B, which are only
-// accessed precisely once and should thus not pollute the L2 cache which we
-// need for inputs A and outputs C.
-__device__ inline void cp_async4_stream(void *smem_ptr, const void *glob_ptr) {
+// Asynchronous global->shared copy
+__device__ inline void cp_async4(void *smem_ptr, const void *glob_ptr) {
   const int BYTES = 16;
   uint32_t smem = static_cast<uint32_t>(__cvta_generic_to_shared(smem_ptr));
-  asm volatile(
-      "{\n"
-      "   .reg .b64 p;\n"
-      "   createpolicy.fractional.L2::evict_first.b64 p, 1.0;"
-      "   cp.async.cg.shared.global.L2::cache_hint [%0], [%1], %2, p;\n"
-      "}\n" ::"r"(smem),
-      "l"(glob_ptr), "n"(BYTES));
+  asm volatile("{\n"
+               "   cp.async.cg.shared.global [%0], [%1], %2;\n"
+               "}\n" :: "r"(smem), "l"(glob_ptr), "n"(BYTES));
 }
 
 // Async copy fence.
@@ -448,14 +441,14 @@ Marlin(const int4 *__restrict__ A, // fp16 input matrix of shape mxk
       int4 *sh_b_stage = sh_b + b_sh_stage * pipe;
 #pragma unroll
       for (int i = 0; i < b_sh_wr_iters; i++) {
-        cp_async4_stream(&sh_b_stage[b_sh_wr_delta * i + b_sh_wr], B_ptr[i]);
+        cp_async4(&sh_b_stage[b_sh_wr_delta * i + b_sh_wr], B_ptr[i]);
         B_ptr[i] += b_gl_rd_delta_o;
       }
       // Only fetch scales if this tile starts a new group
       if (group_blocks != -1 && pipe % (group_blocks / thread_k_blocks) == 0) {
         int4 *sh_s_stage = sh_s + s_sh_stage * pipe;
         if (s_sh_wr_pred)
-          cp_async4_stream(&sh_s_stage[s_sh_wr], &s[s_gl_rd]);
+          cp_async4(&sh_s_stage[s_sh_wr], &s[s_gl_rd]);
         s_gl_rd += s_gl_rd_delta;
       }
     }
@@ -750,7 +743,7 @@ Marlin(const int4 *__restrict__ A, // fp16 input matrix of shape mxk
       // write-out
       if (group_blocks == -1 && last) {
         if (s_sh_wr_pred)
-          cp_async4_stream(&sh_s[s_sh_wr], &s[s_gl_rd]);
+          cp_async4(&sh_s[s_sh_wr], &s[s_gl_rd]);
         cp_async_fence();
       }
       thread_block_reduce();