[PATCH v4 1/2] gpudev: expose GPU memory to CPU

[<eagostini@nvidia.com>]

From: Elena Agostini <eagostini@nvidia.com>

Enable the possibility to expose a GPU memory area and make it
accessible from the CPU.

GPU memory has to be allocated via rte_gpu_mem_alloc().

This patch allows the gpudev library to map (and unmap),
through the GPU driver, a chunk of GPU memory and to return
a memory pointer usable by the CPU to access the GPU memory area.

Signed-off-by: Elena Agostini <eagostini@nvidia.com>
---
 doc/guides/prog_guide/gpudev.rst |  9 +++++
 drivers/gpu/cuda/cuda.c          |  2 ++
 lib/gpudev/gpudev.c              | 61 ++++++++++++++++++++++++++++++++
 lib/gpudev/gpudev_driver.h       |  6 ++++
 lib/gpudev/rte_gpudev.h          | 49 +++++++++++++++++++++++++
 lib/gpudev/version.map           |  2 ++
 6 files changed, 129 insertions(+)

diff --git a/doc/guides/prog_guide/gpudev.rst b/doc/guides/prog_guide/gpudev.rst
index ff4626812b..b774ec77f9 100644
--- a/doc/guides/prog_guide/gpudev.rst
+++ b/doc/guides/prog_guide/gpudev.rst
@@ -73,6 +73,15 @@ Later, it's also possible to unregister that memory with gpudev.
 CPU memory registered outside of the gpudev library
 (e.g. with GPU specific library) cannot be unregistered by the gpudev library.
 
+CPU mapping
+~~~~~~~~~~~~~~~~~~~
+
+gpudev can map into the CPU address space a GPU memory address allocated with gpudev.
+gpudev returns a pointer the CPU can use to access (ready or write) GPU memory.
+Later, it's also possible to unmap that memory with gpudev.
+GPU memory CPU mapped outside of the gpudev library (e.g. with GPU specific library)
+cannot be unmapped by the gpudev library.
+
 Memory Barrier
 ~~~~~~~~~~~~~~
 
diff --git a/drivers/gpu/cuda/cuda.c b/drivers/gpu/cuda/cuda.c
index 0ece1bb612..408b659fce 100644
--- a/drivers/gpu/cuda/cuda.c
+++ b/drivers/gpu/cuda/cuda.c
@@ -1177,6 +1177,8 @@ cuda_gpu_probe(__rte_unused struct rte_pci_driver *pci_drv, struct rte_pci_devic
 	dev->ops.mem_free = cuda_mem_free;
 	dev->ops.mem_register = cuda_mem_register;
 	dev->ops.mem_unregister = cuda_mem_unregister;
+	dev->ops.mem_cpu_map = NULL;
+	dev->ops.mem_cpu_unmap = NULL;
 	dev->ops.wmb = cuda_wmb;
 
 	rte_gpu_complete_new(dev);
diff --git a/lib/gpudev/gpudev.c b/lib/gpudev/gpudev.c
index 59e2169292..ce92d63257 100644
--- a/lib/gpudev/gpudev.c
+++ b/lib/gpudev/gpudev.c
@@ -640,6 +640,67 @@ rte_gpu_mem_unregister(int16_t dev_id, void *ptr)
 	return GPU_DRV_RET(dev->ops.mem_unregister(dev, ptr));
 }
 
+void *
+rte_gpu_mem_cpu_map(int16_t dev_id, size_t size, void *ptr)
+{
+	struct rte_gpu *dev;
+	void *ptr_out;
+	int ret;
+
+	dev = gpu_get_by_id(dev_id);
+	if (dev == NULL) {
+		GPU_LOG(ERR, "mem CPU map for invalid device ID %d", dev_id);
+		rte_errno = ENODEV;
+		return NULL;
+	}
+
+	if (dev->ops.mem_cpu_map == NULL) {
+		GPU_LOG(ERR, "mem CPU map not supported");
+		rte_errno = ENOTSUP;
+		return NULL;
+	}
+
+	if (ptr == NULL || size == 0) /* dry-run  */
+		return NULL;
+
+	ret = GPU_DRV_RET(dev->ops.mem_cpu_map(dev, size, ptr, &ptr_out));
+
+	switch (ret) {
+	case 0:
+		return ptr_out;
+	case -ENOMEM:
+	case -E2BIG:
+		rte_errno = -ret;
+		return NULL;
+	default:
+		rte_errno = -EPERM;
+		return NULL;
+	}
+}
+
+int
+rte_gpu_mem_cpu_unmap(int16_t dev_id, void *ptr)
+{
+	struct rte_gpu *dev;
+
+	dev = gpu_get_by_id(dev_id);
+	if (dev == NULL) {
+		GPU_LOG(ERR, "cpu_unmap mem for invalid device ID %d", dev_id);
+		rte_errno = ENODEV;
+		return -rte_errno;
+	}
+
+	if (dev->ops.mem_cpu_unmap == NULL) {
+		rte_errno = ENOTSUP;
+		return -rte_errno;
+	}
+
+	if (ptr == NULL) /* dry-run */
+		return 0;
+
+	return GPU_DRV_RET(dev->ops.mem_cpu_unmap(dev, ptr));
+}
+
 int
 rte_gpu_wmb(int16_t dev_id)
 {
diff --git a/lib/gpudev/gpudev_driver.h b/lib/gpudev/gpudev_driver.h
index 0ed7478e9b..0e55b00bfe 100644
--- a/lib/gpudev/gpudev_driver.h
+++ b/lib/gpudev/gpudev_driver.h
@@ -31,6 +31,8 @@ typedef int (rte_gpu_mem_alloc_t)(struct rte_gpu *dev, size_t size, unsigned int
 typedef int (rte_gpu_mem_free_t)(struct rte_gpu *dev, void *ptr);
 typedef int (rte_gpu_mem_register_t)(struct rte_gpu *dev, size_t size, void *ptr);
 typedef int (rte_gpu_mem_unregister_t)(struct rte_gpu *dev, void *ptr);
+typedef int (rte_gpu_mem_cpu_map_t)(struct rte_gpu *dev, size_t size, void *ptr_in, void **ptr_out);
+typedef int (rte_gpu_mem_cpu_unmap_t)(struct rte_gpu *dev, void *ptr);
 typedef int (rte_gpu_wmb_t)(struct rte_gpu *dev);
 
 struct rte_gpu_ops {
@@ -46,6 +48,10 @@ struct rte_gpu_ops {
 	rte_gpu_mem_register_t *mem_register;
 	/* Unregister CPU memory from device. */
 	rte_gpu_mem_unregister_t *mem_unregister;
+	/* Map GPU memory for CPU visibility. */
+	rte_gpu_mem_cpu_map_t *mem_cpu_map;
+	/* Unmap GPU memory for CPU visibility. */
+	rte_gpu_mem_cpu_unmap_t *mem_cpu_unmap;
 	/* Enforce GPU write memory barrier. */
 	rte_gpu_wmb_t *wmb;
 };
diff --git a/lib/gpudev/rte_gpudev.h b/lib/gpudev/rte_gpudev.h
index ff3ca78c89..5cc4eb5828 100644
--- a/lib/gpudev/rte_gpudev.h
+++ b/lib/gpudev/rte_gpudev.h
@@ -452,6 +452,55 @@ int rte_gpu_mem_register(int16_t dev_id, size_t size, void *ptr);
 __rte_experimental
 int rte_gpu_mem_unregister(int16_t dev_id, void *ptr);
 
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Map a chunk of GPU memory to make it accessible from the CPU
+ * using the memory pointer returned by the function.
+ * GPU memory has to be allocated via rte_gpu_mem_alloc().
+ *
+ * @param dev_id
+ *   Device ID requiring mapped memory.
+ * @param size
+ *   Number of bytes to map.
+ *   Requesting 0 will do nothing.
+ * @param ptr
+ *   Pointer to the GPU memory area to be mapped.
+ *   NULL is a no-op accepted value.
+
+ * @return
+ *   A pointer to the mapped GPU memory usable by the CPU, otherwise NULL and rte_errno is set:
+ *   - ENODEV if invalid dev_id
+ *   - ENOTSUP if operation not supported by the driver
+ *   - E2BIG if size is higher than limit
+ *   - ENOMEM if out of space
+ *   - EPERM if driver error
+ */
+__rte_experimental
+void *rte_gpu_mem_cpu_map(int16_t dev_id, size_t size, void *ptr);
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice.
+ *
+ * Unmap a chunk of GPU memory previously mapped with rte_gpu_mem_cpu_map()
+ *
+ * @param dev_id
+ *   Reference device ID.
+ * @param ptr
+ *   Pointer to the memory area to be unmapped.
+ *   NULL is a no-op accepted value.
+ *
+ * @return
+ *   0 on success, -rte_errno otherwise:
+ *   - ENODEV if invalid dev_id
+ *   - ENOTSUP if operation not supported by the driver
+ *   - EPERM if driver error
+ */
+__rte_experimental
+int rte_gpu_mem_cpu_unmap(int16_t dev_id, void *ptr);
+
 /**
  * @warning
  * @b EXPERIMENTAL: this API may change without prior notice.
diff --git a/lib/gpudev/version.map b/lib/gpudev/version.map
index 2e414c65cc..5bc5d154cd 100644
--- a/lib/gpudev/version.map
+++ b/lib/gpudev/version.map
@@ -20,8 +20,10 @@ EXPERIMENTAL {
 	rte_gpu_init;
 	rte_gpu_is_valid;
 	rte_gpu_mem_alloc;
+	rte_gpu_mem_cpu_map;
 	rte_gpu_mem_free;
 	rte_gpu_mem_register;
+	rte_gpu_mem_cpu_unmap;
 	rte_gpu_mem_unregister;
 	rte_gpu_wmb;
 };
-- 
2.17.1