Subject: [PATCH 3/5] vDPA: introduce vDPA bus

From: Jason Wang <[email-masked]>
Date: Thu, 16 Jan 2020 20:42:29 +0800

vDPA device is a device that uses a datapath which complies with the
virtio specifications with vendor specific control path. vDPA devices
can be both physically located on the hardware or emulated by
software. vDPA hardware devices are usually implemented through PCIE
with the following types:

- PF (Physical Function) - A single Physical Function
- VF (Virtual Function) - Device that supports single root I/O
  virtualization (SR-IOV). Its Virtual Function (VF) represents a
  virtualized instance of the device that can be assigned to different
  partitions
- VDEV (Virtual Device) - With technologies such as Intel Scalable
  IOV, a virtual device composed by host OS utilizing one or more
  ADIs.
- SF (Sub function) - Vendor specific interface to slice the Physical
  Function to multiple sub functions that can be assigned to different
  partitions as virtual devices.

>From a driver's perspective, depends on how and where the DMA
translation is done, vDPA devices are split into two types:

- Platform specific DMA translation - From the driver's perspective,
  the device can be used on a platform where device access to data in
  memory is limited and/or translated. An example is a PCIE vDPA whose
  DMA request was tagged via a bus (e.g PCIE) specific way. DMA
  translation and protection are done at PCIE bus IOMMU level.
- Device specific DMA translation - The device implements DMA
  isolation and protection through its own logic. An example is a vDPA
  device which uses on-chip IOMMU.

To hide the differences and complexity of the above types for a vDPA
device/IOMMU options and in order to present a generic virtio device
to the upper layer, a device agnostic framework is required.

This patch introduces a software vDPA bus which abstracts the
common attributes of vDPA device, vDPA bus driver and the
communication method (vdpa_config_ops) between the vDPA device
abstraction and the vDPA bus driver:

With the abstraction of vDPA bus and vDPA bus operations, the
difference and complexity of the under layer hardware is hidden from
upper layer. The vDPA bus drivers on top can use a unified
vdpa_config_ops to control different types of vDPA device.

Signed-off-by: Jason Wang <[email-masked]>
---
 MAINTAINERS                  |   1 +
 drivers/virtio/Kconfig       |   2 +
 drivers/virtio/Makefile      |   1 +
 drivers/virtio/vdpa/Kconfig  |   9 ++
 drivers/virtio/vdpa/Makefile |   2 +
 drivers/virtio/vdpa/vdpa.c   | 141 ++++++++++++++++++++++++++
 include/linux/vdpa.h         | 191 +++++++++++++++++++++++++++++++++++
 7 files changed, 347 insertions(+)
 create mode 100644 drivers/virtio/vdpa/Kconfig
 create mode 100644 drivers/virtio/vdpa/Makefile
 create mode 100644 drivers/virtio/vdpa/vdpa.c
 create mode 100644 include/linux/vdpa.h

diff --git a/MAINTAINERS b/MAINTAINERS
index d4bda9c900fa..578d2a581e3b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17540,6 +17540,7 @@ F:	tools/virtio/
 F:	drivers/net/virtio_net.c
 F:	drivers/block/virtio_blk.c
 F:	include/linux/virtio*.h
+F:	include/linux/vdpa.h
 F:	include/uapi/linux/virtio_*.h
 F:	drivers/crypto/virtio/
 F:	mm/balloon_compaction.c
diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 078615cf2afc..9c4fdb64d9ac 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -96,3 +96,5 @@ config VIRTIO_MMIO_CMDLINE_DEVICES
 	 If unsure, say 'N'.
 
 endif # VIRTIO_MENU
+
+source "drivers/virtio/vdpa/Kconfig"
diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
index 3a2b5c5dcf46..fdf5eacd0d0a 100644
--- a/drivers/virtio/Makefile
+++ b/drivers/virtio/Makefile
@@ -6,3 +6,4 @@ virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o
 virtio_pci-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
 obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o
+obj-$(CONFIG_VDPA) += vdpa/
diff --git a/drivers/virtio/vdpa/Kconfig b/drivers/virtio/vdpa/Kconfig
new file mode 100644
index 000000000000..3032727b4d98
--- /dev/null
+++ b/drivers/virtio/vdpa/Kconfig
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config VDPA
+	tristate
+        default n
+        help
+          Enable this module to support vDPA device that uses a
+          datapath which complies with virtio specifications with
+          vendor specific control path.
+
diff --git a/drivers/virtio/vdpa/Makefile b/drivers/virtio/vdpa/Makefile
new file mode 100644
index 000000000000..ee6a35e8a4fb
--- /dev/null
+++ b/drivers/virtio/vdpa/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_VDPA) += vdpa.o
diff --git a/drivers/virtio/vdpa/vdpa.c b/drivers/virtio/vdpa/vdpa.c
new file mode 100644
index 000000000000..2b0e4a9f105d
--- /dev/null
+++ b/drivers/virtio/vdpa/vdpa.c
@@ -0,0 +1,141 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * vDPA bus.
+ *
+ * Copyright (c) 2019, Red Hat. All rights reserved.
+ *     Author: Jason Wang <[email-masked]>
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/idr.h>
+#include <linux/vdpa.h>
+
+#define MOD_VERSION  "0.1"
+#define MOD_DESC     "vDPA bus"
+#define MOD_AUTHOR   "Jason Wang <[email-masked]>"
+#define MOD_LICENSE  "GPL v2"
+
+static DEFINE_IDA(vdpa_index_ida);
+
+struct device *vdpa_get_parent(struct vdpa_device *vdpa)
+{
+	return vdpa->dev.parent;
+}
+EXPORT_SYMBOL(vdpa_get_parent);
+
+void vdpa_set_parent(struct vdpa_device *vdpa, struct device *parent)
+{
+	vdpa->dev.parent = parent;
+}
+EXPORT_SYMBOL(vdpa_set_parent);
+
+struct vdpa_device *dev_to_vdpa(struct device *_dev)
+{
+	return container_of(_dev, struct vdpa_device, dev);
+}
+EXPORT_SYMBOL_GPL(dev_to_vdpa);
+
+struct device *vdpa_to_dev(struct vdpa_device *vdpa)
+{
+	return &vdpa->dev;
+}
+EXPORT_SYMBOL_GPL(vdpa_to_dev);
+
+static int vdpa_dev_probe(struct device *d)
+{
+	struct vdpa_device *dev = dev_to_vdpa(d);
+	struct vdpa_driver *drv = drv_to_vdpa(dev->dev.driver);
+	int ret = 0;
+
+	if (drv && drv->probe)
+		ret = drv->probe(d);
+
+	return ret;
+}
+
+static int vdpa_dev_remove(struct device *d)
+{
+	struct vdpa_device *dev = dev_to_vdpa(d);
+	struct vdpa_driver *drv = drv_to_vdpa(dev->dev.driver);
+
+	if (drv && drv->remove)
+		drv->remove(d);
+
+	return 0;
+}
+
+static struct bus_type vdpa_bus = {
+	.name  = "vdpa",
+	.probe = vdpa_dev_probe,
+	.remove = vdpa_dev_remove,
+};
+
+int register_vdpa_device(struct vdpa_device *vdpa)
+{
+	int err;
+
+	if (!vdpa_get_parent(vdpa))
+		return -EINVAL;
+
+	if (!vdpa->config)
+		return -EINVAL;
+
+	err = ida_simple_get(&vdpa_index_ida, 0, 0, GFP_KERNEL);
+	if (err < 0)
+		return -EFAULT;
+
+	vdpa->dev.bus = &vdpa_bus;
+	device_initialize(&vdpa->dev);
+
+	vdpa->index = err;
+	dev_set_name(&vdpa->dev, "vdpa%u", vdpa->index);
+
+	err = device_add(&vdpa->dev);
+	if (err)
+		ida_simple_remove(&vdpa_index_ida, vdpa->index);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(register_vdpa_device);
+
+void unregister_vdpa_device(struct vdpa_device *vdpa)
+{
+	int index = vdpa->index;
+
+	device_unregister(&vdpa->dev);
+	ida_simple_remove(&vdpa_index_ida, index);
+}
+EXPORT_SYMBOL_GPL(unregister_vdpa_device);
+
+int register_vdpa_driver(struct vdpa_driver *driver)
+{
+	driver->drv.bus = &vdpa_bus;
+	return driver_register(&driver->drv);
+}
+EXPORT_SYMBOL_GPL(register_vdpa_driver);
+
+void unregister_vdpa_driver(struct vdpa_driver *driver)
+{
+	driver_unregister(&driver->drv);
+}
+EXPORT_SYMBOL_GPL(unregister_vdpa_driver);
+
+static int vdpa_init(void)
+{
+	if (bus_register(&vdpa_bus) != 0)
+		panic("virtio bus registration failed");
+	return 0;
+}
+
+static void __exit vdpa_exit(void)
+{
+	bus_unregister(&vdpa_bus);
+	ida_destroy(&vdpa_index_ida);
+}
+core_initcall(vdpa_init);
+module_exit(vdpa_exit);
+
+MODULE_VERSION(MOD_VERSION);
+MODULE_AUTHOR(MOD_AUTHOR);
+MODULE_LICENSE(MOD_LICENSE);
diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
new file mode 100644
index 000000000000..47760137ef66
--- /dev/null
+++ b/include/linux/vdpa.h
@@ -0,0 +1,191 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_VDPA_H
+#define _LINUX_VDPA_H
+
+#include <linux/device.h>
+#include <linux/interrupt.h>
+#include <linux/vhost_iotlb.h>
+
+/**
+ * vDPA callback definition.
+ * @callback: interrupt callback function
+ * @private: the data passed to the callback function
+ */
+struct vdpa_callback {
+	irqreturn_t (*callback)(void *data);
+	void *private;
+};
+
+/**
+ * vDPA device - representation of a vDPA device
+ * @dev: underlying device
+ * @config: the configuration ops for this device.
+ * @index: device index
+ */
+struct vdpa_device {
+	struct device dev;
+	const struct vdpa_config_ops *config;
+	int index;
+};
+
+/**
+ * vDPA_config_ops - operations for configuring a vDPA device.
+ * Note: vDPA device drivers are required to implement all of the
+ * operations unless it is optional mentioned in the following list.
+ * @set_vq_address:		Set the address of virtqueue
+ *				@vdev: vdpa device
+ *				@idx: virtqueue index
+ *				@desc_area: address of desc area
+ *				@driver_area: address of driver area
+ *				@device_area: address of device area
+ *				Returns integer: success (0) or error (< 0)
+ * @set_vq_num:			Set the size of virtqueue
+ *				@vdev: vdpa device
+ *				@idx: virtqueue index
+ *				@num: the size of virtqueue
+ * @kick_vq:			Kick the virtqueue
+ *				@vdev: vdpa device
+ *				@idx: virtqueue index
+ * @set_vq_cb:			Set the interrupt callback function for
+ *				a virtqueue
+ *				@vdev: vdpa device
+ *				@idx: virtqueue index
+ *				@cb: virtio-vdev interrupt callback structure
+ * @set_vq_ready:		Set ready status for a virtqueue
+ *				@vdev: vdpa device
+ *				@idx: virtqueue index
+ *				@ready: ready (true) not ready(false)
+ * @get_vq_ready:		Get ready status for a virtqueue
+ *				@vdev: vdpa device
+ *				@idx: virtqueue index
+ *				Returns boolean: ready (true) or not (false)
+ * @set_vq_state:		Set the state for a virtqueue
+ *				@vdev: vdpa device
+ *				@idx: virtqueue index
+ *				@state: virtqueue state (last_avail_idx)
+ *				Returns integer: success (0) or error (< 0)
+ * @get_vq_state:		Get the state for a virtqueue
+ *				@vdev: vdpa device
+ *				@idx: virtqueue index
+ *				Returns virtqueue state (last_avail_idx)
+ * @get_vq_align:		Get the virtqueue align requirement
+ *				for the device
+ *				@vdev: vdpa device
+ *				Returns virtqueue algin requirement
+ * @get_features:		Get virtio features supported by the device
+ *				@vdev: vdpa device
+ *				Returns the virtio features support by the
+ *				device
+ * @set_features:		Set virtio features supported by the driver
+ *				@vdev: vdpa device
+ *				@features: feature support by the driver
+ *				Returns integer: success (0) or error (< 0)
+ * @set_config_cb:		Set the config interrupt callback
+ *				@vdev: vdpa device
+ *				@cb: virtio-vdev interrupt callback structure
+ * @get_vq_num_max:		Get the max size of virtqueue
+ *				@vdev: vdpa device
+ *				Returns u16: max size of virtqueue
+ * @get_device_id:		Get virtio device id
+ *				@vdev: vdpa device
+ *				Returns u32: virtio device id
+ * @get_vendor_id:		Get id for the vendor that provides this device
+ *				@vdev: vdpa device
+ *				Returns u32: virtio vendor id
+ * @get_status:			Get the device status
+ *				@vdev: vdpa device
+ *				Returns u8: virtio device status
+ * @set_status:			Set the device status
+ *				@vdev: vdpa device
+ *				@status: virtio device status
+ * @get_config:			Read from device specific configuration space
+ *				@vdev: vdpa device
+ *				@offset: offset from the beginning of
+ *				configuration space
+ *				@buf: buffer used to read to
+ *				@len: the length to read from
+ *				configuration space
+ * @set_config:			Write to device specific configuration space
+ *				@vdev: vdpa device
+ *				@offset: offset from the beginning of
+ *				configuration space
+ *				@buf: buffer used to write from
+ *				@len: the length to write to
+ *				configuration space
+ * @get_generation:		Get device config generation (optional)
+ *				@vdev: vdpa device
+ *				Returns u32: device generation
+ * @set_map:			Set device memory mapping, optional
+ *				and only needed for device that using
+ *				device specific DMA translation
+ *				(on-chip IOMMU)
+ *				@vdev: vdpa device
+ *				@iotlb: vhost memory mapping to be
+ *				used by the vDPA
+ *				Returns integer: success (0) or error (< 0)
+ */
+struct vdpa_config_ops {
+	/* Virtqueue ops */
+	int (*set_vq_address)(struct vdpa_device *vdev,
+			      u16 idx, u64 desc_area, u64 driver_area,
+			      u64 device_area);
+	void (*set_vq_num)(struct vdpa_device *vdev, u16 idx, u32 num);
+	void (*kick_vq)(struct vdpa_device *vdev, u16 idx);
+	void (*set_vq_cb)(struct vdpa_device *vdev, u16 idx,
+			  struct vdpa_callback *cb);
+	void (*set_vq_ready)(struct vdpa_device *vdev, u16 idx, bool ready);
+	bool (*get_vq_ready)(struct vdpa_device *vdev, u16 idx);
+	int (*set_vq_state)(struct vdpa_device *vdev, u16 idx, u64 state);
+	u64 (*get_vq_state)(struct vdpa_device *vdev, u16 idx);
+
+	/* Device ops */
+	u16 (*get_vq_align)(struct vdpa_device *vdev);
+	u64 (*get_features)(struct vdpa_device *vdev);
+	int (*set_features)(struct vdpa_device *vdev, u64 features);
+	void (*set_config_cb)(struct vdpa_device *vdev,
+			      struct vdpa_callback *cb);
+	u16 (*get_vq_num_max)(struct vdpa_device *vdev);
+	u32 (*get_device_id)(struct vdpa_device *vdev);
+	u32 (*get_vendor_id)(struct vdpa_device *vdev);
+	u8 (*get_status)(struct vdpa_device *vdev);
+	void (*set_status)(struct vdpa_device *vdev, u8 status);
+	void (*get_config)(struct vdpa_device *vdev, unsigned int offset,
+			   void *buf, unsigned int len);
+	void (*set_config)(struct vdpa_device *vdev, unsigned int offset,
+			   const void *buf, unsigned int len);
+	u32 (*get_generation)(struct vdpa_device *vdev);
+
+	/* Mem table */
+	int (*set_map)(struct vdpa_device *vdev, struct vhost_iotlb *iotlb);
+};
+
+int register_vdpa_device(struct vdpa_device *vdpa);
+void unregister_vdpa_device(struct vdpa_device *vdpa);
+
+struct device *vdpa_get_parent(struct vdpa_device *vdpa);
+void vdpa_set_parent(struct vdpa_device *vdpa, struct device *parent);
+
+struct vdpa_device *dev_to_vdpa(struct device *_dev);
+struct device *vdpa_to_dev(struct vdpa_device *vdpa);
+
+/**
+ * vdpa_driver - operations for a vDPA driver
+ * @driver: underlying device driver
+ * @probe: the function to call when a device is found.  Returns 0 or -errno.
+ * @remove: the function to call when a device is removed.
+ */
+struct vdpa_driver {
+	struct device_driver drv;
+	int (*probe)(struct device *dev);
+	void (*remove)(struct device *dev);
+};
+
+int register_vdpa_driver(struct vdpa_driver *drv);
+void unregister_vdpa_driver(struct vdpa_driver *drv);
+
+static inline struct vdpa_driver *drv_to_vdpa(struct device_driver *drv)
+{
+	return container_of(drv, struct vdpa_driver, drv);
+}
+
+#endif /* _LINUX_VDPA_H */
-- 
2.19.1