drm/amdkfd: CRIU export BOs as prime dmabuf objects

KFD buffer objects do not associate a GEM handle with them so cannot
directly be used with libdrm to initiate a system dma (sDMA) operation
to speedup the checkpoint and restore operation so export them as dmabuf
objects and use with libdrm helper (amdgpu_bo_import) to further process
the sdma command submissions.

With sDMA, we see huge improvement in checkpoint and restore operations
compared to the generic pci based access via host data path.
Suggested-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@amd.com>
Signed-off-by: David Yat Sin <david.yatsin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -35,6 +35,7 @@
 #include <linux/mman.h>
 #include <linux/ptrace.h>
 #include <linux/dma-buf.h>
+#include <linux/fdtable.h>
 #include <asm/processor.h>
 #include "kfd_priv.h"
 #include "kfd_device_queue_manager.h"
@@ -42,6 +43,7 @@
 #include "kfd_svm.h"
 #include "amdgpu_amdkfd.h"
 #include "kfd_smi_events.h"
+#include "amdgpu_dma_buf.h"
 
 static long kfd_ioctl(struct file *, unsigned int, unsigned long);
 static int kfd_open(struct inode *, struct file *);
@@ -1936,6 +1938,33 @@ uint32_t get_process_num_bos(struct kfd_process *p)
 	return num_of_bos;
 }
 
+static int criu_get_prime_handle(struct drm_gem_object *gobj, int flags,
+				      u32 *shared_fd)
+{
+	struct dma_buf *dmabuf;
+	int ret;
+
+	dmabuf = amdgpu_gem_prime_export(gobj, flags);
+	if (IS_ERR(dmabuf)) {
+		ret = PTR_ERR(dmabuf);
+		pr_err("dmabuf export failed for the BO\n");
+		return ret;
+	}
+
+	ret = dma_buf_fd(dmabuf, flags);
+	if (ret < 0) {
+		pr_err("dmabuf create fd failed, ret:%d\n", ret);
+		goto out_free_dmabuf;
+	}
+
+	*shared_fd = ret;
+	return 0;
+
+out_free_dmabuf:
+	dma_buf_put(dmabuf);
+	return ret;
+}
+
 static int criu_checkpoint_bos(struct kfd_process *p,
 			       uint32_t num_bos,
 			       uint8_t __user *user_bos,
@@ -1997,6 +2026,14 @@ static int criu_checkpoint_bos(struct kfd_process *p,
 					goto exit;
 				}
 			}
+			if (bo_bucket->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_VRAM) {
+				ret = criu_get_prime_handle(&dumper_bo->tbo.base,
+						bo_bucket->alloc_flags &
+						KFD_IOC_ALLOC_MEM_FLAGS_WRITABLE ? DRM_RDWR : 0,
+						&bo_bucket->dmabuf_fd);
+				if (ret)
+					goto exit;
+			}
 			if (bo_bucket->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_DOORBELL)
 				bo_bucket->offset = KFD_MMAP_TYPE_DOORBELL |
 					KFD_MMAP_GPU_ID(pdd->dev->id);
@@ -2041,6 +2078,10 @@ static int criu_checkpoint_bos(struct kfd_process *p,
 	*priv_offset += num_bos * sizeof(*bo_privs);
 
 exit:
+	while (ret && bo_index--) {
+		if (bo_buckets[bo_index].alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_VRAM)
+			close_fd(bo_buckets[bo_index].dmabuf_fd);
+	}
 
 	kvfree(bo_buckets);
 	kvfree(bo_privs);
@@ -2141,16 +2182,28 @@ static int criu_checkpoint(struct file *filep,
 		ret = kfd_criu_checkpoint_queues(p, (uint8_t __user *)args->priv_data,
 						 &priv_offset);
 		if (ret)
-			goto exit_unlock;
+			goto close_bo_fds;
 
 		ret = kfd_criu_checkpoint_events(p, (uint8_t __user *)args->priv_data,
 						 &priv_offset);
 		if (ret)
-			goto exit_unlock;
+			goto close_bo_fds;
 
 		/* TODO: Dump SVM-Ranges */
 	}
 
+close_bo_fds:
+	if (ret) {
+		/* If IOCTL returns err, user assumes all FDs opened in criu_dump_bos are closed */
+		uint32_t i;
+		struct kfd_criu_bo_bucket *bo_buckets = (struct kfd_criu_bo_bucket *) args->bos;
+
+		for (i = 0; i < num_bos; i++) {
+			if (bo_buckets[i].alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_VRAM)
+				close_fd(bo_buckets[i].dmabuf_fd);
+		}
+	}
+
 exit_unlock:
 	mutex_unlock(&p->mutex);
 	if (ret)
@@ -2345,6 +2398,7 @@ static int criu_restore_bos(struct kfd_process *p,
 		struct kfd_criu_bo_priv_data *bo_priv;
 		struct kfd_dev *dev;
 		struct kfd_process_device *pdd;
+		struct kgd_mem *kgd_mem;
 		void *mem;
 		u64 offset;
 		int idr_handle;
@@ -2484,6 +2538,15 @@ static int criu_restore_bos(struct kfd_process *p,
 		}
 
 		pr_debug("map memory was successful for the BO\n");
+		/* create the dmabuf object and export the bo */
+		kgd_mem = (struct kgd_mem *)mem;
+		if (bo_bucket->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_VRAM) {
+			ret = criu_get_prime_handle(&kgd_mem->bo->tbo.base,
+						    DRM_RDWR,
+						    &bo_bucket->dmabuf_fd);
+			if (ret)
+				goto exit;
+		}
 	} /* done */
 
 	if (flush_tlbs) {
@@ -2511,6 +2574,10 @@ static int criu_restore_bos(struct kfd_process *p,
 		ret = -EFAULT;
 
 exit:
+	while (ret && i--) {
+		if (bo_buckets[i].alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_VRAM)
+			close_fd(bo_buckets[i].dmabuf_fd);
+	}
 	kvfree(bo_buckets);
 	kvfree(bo_privs);
 	return ret;