drm/amdkfd: Add module option for testing large-BAR functionality

Simulate large-BAR system by exporting only visible memory. This
limits the amount of available VRAM to the size of the BAR, but
enables CPU access to VRAM.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

drivers/gpu/drm/amd/amdkfd/kfd_chardev.c

@@ -1151,6 +1151,11 @@ bool kfd_dev_is_large_bar(struct kfd_dev *dev)
 {
 	struct kfd_local_mem_info mem_info;
 
+	if (debug_largebar) {
+		pr_debug("Simulate large-bar allocation on non large-bar machine\n");
+		return true;
+	}
+
 	if (dev->device_info->needs_iommu_device)
 		return false;
 

drivers/gpu/drm/amd/amdkfd/kfd_crat.c

@@ -1117,6 +1117,9 @@ static int kfd_create_vcrat_image_gpu(void *pcrat_image,
 	sub_type_hdr = (typeof(sub_type_hdr))((char *)sub_type_hdr +
 			sub_type_hdr->length);
 
+	if (debug_largebar)
+		local_mem_info.local_mem_size_private = 0;
+
 	if (local_mem_info.local_mem_size_private == 0)
 		ret = kfd_fill_gpu_memory_affinity(&avail_size,
 				kdev, HSA_MEM_HEAP_TYPE_FB_PUBLIC,

drivers/gpu/drm/amd/amdkfd/kfd_module.c

@@ -71,6 +71,11 @@ module_param(send_sigterm, int, 0444);
 MODULE_PARM_DESC(send_sigterm,
 	"Send sigterm to HSA process on unhandled exception (0 = disable, 1 = enable)");
 
+int debug_largebar;
+module_param(debug_largebar, int, 0444);
+MODULE_PARM_DESC(debug_largebar,
+	"Debug large-bar flag used to simulate large-bar capability on non-large bar machine (0 = disable, 1 = enable)");
+
 int ignore_crat;
 module_param(ignore_crat, int, 0444);
 MODULE_PARM_DESC(ignore_crat,

drivers/gpu/drm/amd/amdkfd/kfd_priv.h

@@ -104,6 +104,12 @@ extern int cwsr_enable;
  */
 extern int send_sigterm;
 
+/*
+ * This kernel module is used to simulate large bar machine on non-large bar
+ * enabled machines.
+ */
+extern int debug_largebar;
+
 /*
  * Ignore CRAT table during KFD initialization, can be used to work around
  * broken CRAT tables on some AMD systems