[PATCH 14/14] drm/amdkfd: Add module option for testing large-BAR functionality

[Felix Kuehling]

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 at amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 5 +++++
 drivers/gpu/drm/amd/amdkfd/kfd_crat.c    | 3 +++
 drivers/gpu/drm/amd/amdkfd/kfd_module.c  | 5 +++++
 drivers/gpu/drm/amd/amdkfd/kfd_priv.h    | 6 ++++++
 4 files changed, 19 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
index 222ea97..d7bea8d 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
+++ b/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;
 
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
index 7493f47..3c6c4cdd 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
+++ b/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,
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_module.c b/drivers/gpu/drm/amd/amdkfd/kfd_module.c
index 65574c6..b0acb06 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_module.c
+++ b/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,
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
index aa93863..db27f9f 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
@@ -105,6 +105,12 @@ 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
  */
-- 
2.7.4