[PATCH 1/6] virtio interace

Rusty Russell
2007-09-20T12:09:00Z

(Changes:
- renamed sync to kick as Dor suggested
- added new_vq and free_vq hooks to create virtqueues
- define a simple virtio driver, which uses PCI ids
- provide register/unregister_virtio_driver hooks)

This attempts to implement a "virtual I/O" layer which should allow
common drivers to be efficiently used across most virtual I/O
mechanisms. It will no-doubt need further enhancement.

The virtio drivers add and get I/O buffers; as the buffers are consumed
the driver "interrupt" callbacks are invoked.

It also provides driver register and unregister hooks, which are
simply overridden at run time (eg. for a guest kernel which supports
KVM paravirt and lguest).

Signed-off-by: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
---
drivers/virtio/Kconfig | 3 +
drivers/virtio/Makefile | 1
drivers/virtio/virtio.c | 20 ++++++++
include/linux/virtio.h | 114 +++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 138 insertions(+)

===================================================================
--- /dev/null
+++ b/drivers/virtio/Kconfig
@@ -0,0 +1,3 @@
+# Virtio always gets selected by whoever wants it.
+config VIRTIO
+ bool
===================================================================
--- /dev/null
+++ b/drivers/virtio/Makefile
@@ -0,0 +1,1 @@
+obj-$(CONFIG_VIRTIO) += virtio.o
===================================================================
--- /dev/null
+++ b/drivers/virtio/virtio.c
@@ -0,0 +1,20 @@
+#include <linux/virtio.h>
+
+struct virtio_backend_ops virtio_backend_ops;
+EXPORT_SYMBOL_GPL(virtio_backend_ops);
+
+/* register and unregister simply punt through to the specific backend. */
+int register_virtio_driver(struct virtio_driver *drv)
+{
+ if (!virtio_backend_ops.register_driver)
+ return -ENOSYS;
+
+ return virtio_backend_ops.register_driver(drv);
+}
+EXPORT_SYMBOL_GPL(register_virtio_driver);
+
+void unregister_virtio_driver(struct virtio_driver *drv)
+{
+ virtio_backend_ops.unregister_driver(drv);
+}
+EXPORT_SYMBOL_GPL(unregister_virtio_driver);
===================================================================
--- /dev/null
+++ b/include/linux/virtio.h
@@ -0,0 +1,114 @@
+#ifndef _LINUX_VIRTIO_H
+#define _LINUX_VIRTIO_H
+/* Everything a virtio driver needs to work with any particular virtio
+ * implementation. */
+#include <linux/types.h>
+#include <linux/scatterlist.h>
+#include <linux/spinlock.h>
+#include <linux/pci.h>
+
+struct device;
+struct virtio_config_space;
+
+/**
+ * virtqueue_ops - operations for virtqueue abstraction layer
+ * @new_vq: create a new virtqueue
+ * config: the virtio_config_space field describing the queue
+ * off: the offset in the config space of the queue configuration
+ * len: the length of the virtio_config_space field
+ * callback: the driver callback when the queue is used.
+ * cb_data: the pointer for the callback.
+ * Returns a new virtqueue or an ERR_PTR.
+ * @free_vq: free a virtqueue
+ * vq: the struct virtqueue to free (must be unused or empty).
+ * @add_buf: expose buffer to other end
+ * vq: the struct virtqueue we're talking about.
+ * sg: the description of the buffer(s).
+ * out_num: the number of sg readable by other side
+ * in_num: the number of sg which are writable (after readable ones)
+ * data: the token identifying the buffer.
+ * Returns 0 or an error.
+ * @kick: update after add_buf
+ * vq: the struct virtqueue
+ * After one or more add_buf calls, invoke this to kick the virtio layer.
+ * @get_buf: get the next used buffer
+ * vq: the struct virtqueue we're talking about.
+ * len: the length written into the buffer
+ * Returns NULL or the "data" token handed to add_buf.
+ * @restart: restart callbacks ater callback returned false.
+ * vq: the struct virtqueue we're talking about.
+ * This returns "false" (and doesn't re-enable) if there are pending
+ * buffers in the queue, to avoid a race.
+ * @shutdown: "unadd" all buffers.
+ * vq: the struct virtqueue we're talking about.
+ * Remove everything from the queue.
+ *
+ * Locking rules are straightforward: the driver is responsible for
+ * locking. No two operations may be invoked simultaneously.
+ *
+ * All operations can be called in any context.
+ */
+struct virtqueue_ops {
+ struct virtqueue *(*new_vq)(struct device *dev,
+ struct virtio_config_space *config,
+ int off, unsigned len,
+ bool (*callback)(void *),
+ void *cb_data);
+
+ void (*free_vq)(struct virtqueue *vq);
+
+ int (*add_buf)(struct virtqueue *vq,
+ struct scatterlist sg[],
+ unsigned int out_num,
+ unsigned int in_num,
+ void *data);
+
+ void (*kick)(struct virtqueue *vq);
+
+ void *(*get_buf)(struct virtqueue *vq, unsigned int *len);
+
+ bool (*restart)(struct virtqueue *vq);
+
+ void (*shutdown)(struct virtqueue *vq);
+};
+
+/* FIXME: Get a real PCI vendor ID. */
+#define PCI_VENDOR_ID_VIRTIO 0x5000
+
+#define VIRTIO_DEV_ID(_devid, _class) { \
+ .vendor = PCI_VENDOR_ID_VIRTIO, \
+ .device = (_devid), \
+ .subvendor = PCI_ANY_ID, \
+ .subdevice = PCI_ANY_ID, \
+ .class = (_class)<<8, \
+ .class_mask = 0xFFFF00 }
+
+/**
+ * virtio_driver - operations for a virtio I/O driver
+ * @name: the name of the driver (KBUILD_MODNAME).
+ * @owner: the module which contains these routines (ie. THIS_MODULE).
+ * @id_table: the ids (we re-use PCI ids) serviced by this driver.
+ * @probe: the function to call when a device is found. Returns a token for
+ * remove, or PTR_ERR().
+ * @remove: the function when a device is removed.
+ */
+struct virtio_driver {
+ const char *name;
+ struct module *owner;
+ struct pci_device_id *id_table;
+ void *(*probe)(struct device *device,
+ struct virtio_config_space *config,
+ struct virtqueue_ops *vqops);
+ void (*remove)(void *dev);
+};
+
+int register_virtio_driver(struct virtio_driver *drv);
+void unregister_virtio_driver(struct virtio_driver *drv);
+
+/* The particular virtio backend supplies these. */
+struct virtio_backend_ops {
+ int (*register_driver)(struct virtio_driver *drv);
+ void (*unregister_driver)(struct virtio_driver *drv);
+};
+extern struct virtio_backend_ops virtio_backend_ops;
+#endif /* _LINUX_VIRTIO_H */