[libc-commits] [libc] [libc] Explicitly pin memory for the client symbol lookup (PR #73988)

[via libc-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Joseph Huber (jhuber6)

<details>
<summary>Changes</summary>

Summary:
Previously, we determined that coarse grained memory cannot be used in
the general case. That removed the buffer used to transfer the memory,
however we still had this lookup. Though we do not access the symbol
directly, it still conflicts with the agents apparently. Pin this as
well.

This resolves the problems @<!-- -->lntue was having with the `libc` GPU build.


---
Full diff: https://github.com/llvm/llvm-project/pull/73988.diff


1 Files Affected:

- (modified) libc/utils/gpu/loader/amdgpu/Loader.cpp (+9-7) 


``````````diff
diff --git a/libc/utils/gpu/loader/amdgpu/Loader.cpp b/libc/utils/gpu/loader/amdgpu/Loader.cpp
index 5c28607b2f290a9..a9a687656efcb39 100644
--- a/libc/utils/gpu/loader/amdgpu/Loader.cpp
+++ b/libc/utils/gpu/loader/amdgpu/Loader.cpp
@@ -464,18 +464,20 @@ int load(int argc, char **argv, char **envp, void *image, size_t size,
           executable, rpc_client_symbol_name, &dev_agent, &rpc_client_sym))
     handle_error(err);
 
-  void *rpc_client_host;
-  if (hsa_status_t err =
-          hsa_amd_memory_pool_allocate(coarsegrained_pool, sizeof(void *),
-                                       /*flags=*/0, &rpc_client_host))
-    handle_error(err);
-
   void *rpc_client_dev;
   if (hsa_status_t err = hsa_executable_symbol_get_info(
           rpc_client_sym, HSA_EXECUTABLE_SYMBOL_INFO_VARIABLE_ADDRESS,
           &rpc_client_dev))
     handle_error(err);
 
+  // Pin some memory we can use to obtain the address of the rpc client.
+  void *rpc_client_storage = nullptr;
+  void *rpc_client_host = nullptr;
+  if (hsa_status_t err =
+          hsa_amd_memory_lock(&rpc_client_storage, sizeof(void *),
+                              /*agents=*/nullptr, 0, &rpc_client_host))
+    handle_error(err);
+
   // Copy the address of the client buffer from the device to the host.
   if (hsa_status_t err = hsa_memcpy(rpc_client_host, host_agent, rpc_client_dev,
                                     dev_agent, sizeof(void *)))
@@ -497,7 +499,7 @@ int load(int argc, char **argv, char **envp, void *image, size_t size,
   if (hsa_status_t err = hsa_amd_memory_unlock(
           const_cast<void *>(rpc_get_client_buffer(device_id))))
     handle_error(err);
-  if (hsa_status_t err = hsa_amd_memory_pool_free(rpc_client_host))
+  if (hsa_status_t err = hsa_amd_memory_unlock(rpc_client_host))
     handle_error(err);
 
   // Obtain the GPU's fixed-frequency clock rate and copy it to the GPU.

``````````

</details>


https://github.com/llvm/llvm-project/pull/73988