Draft III of virtio interface 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 details of probing the device are left to hypervisor-specific code: it simple constructs the "struct virtio_device" and hands it to the probe function (eg. virtnet_probe() or virtblk_probe()). The virtio drivers add and get input and output buffers; as the buffers are used up the driver "interrupt" callbacks are invoked. I have written two virtio device drivers (net and block) and two virtio implementations (for lguest): a read-write socket-style implementation, and a more efficient descriptor-based implementation. Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx> --- include/linux/virtio.h | 115 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) =================================================================== --- /dev/null +++ b/include/linux/virtio.h @@ -0,0 +1,115 @@ +#ifndef _LINUX_VIRTIO_H +#define _LINUX_VIRTIO_H +#include <linux/types.h> +#include <linux/scatterlist.h> +#include <linux/spinlock.h> + +/** + * virtio_device - description and routines to drive a virtual device. + * @dev: the underlying struct device. + * @ops: the operations for this virtual device. + * @driver_ops: set by the driver for callbacks. + * @priv: private pointer for the driver to use. + */ +struct virtio_device { + struct device *dev; + struct virtio_ops *ops; + struct virtio_driver_ops *driver_ops; + void *priv; +}; + +/** + * virtio_driver_ops - driver callbacks for a virtual device. + * @in: inbufs have been completed. + * Usually called from an interrupt handler. + * Return false to suppress further inbuf callbacks. + * @out: outbufs have been completed. + * Usually called from an interrupt handler. + * Return false to suppress further outbuf callbacks. + */ +struct virtio_driver_ops { + bool (*in)(struct virtio_device *dev); + bool (*out)(struct virtio_device *dev); +}; + +enum virtio_dir { + VIRTIO_IN = 0x1, + VIRTIO_OUT = 0x2, +}; + +/** + * virtio_ops - virtio abstraction layer + * @add_outbuf: prepare to send data to the other end: + * vdev: the virtio_device + * sg: the description of the buffer(s). + * num: the size of the sg array. + * data: the token returned by the get_outbuf function. + * Returns a unique id or an error. + * @add_inbuf: prepare to receive data from the other end: + * vdev: the virtio_device + * sg: the description of the buffer(s). + * num: the size of the sg array. + * data: the token returned by the get_inbuf function. + * Returns a unique id or an error (eg. -ENOSPC). + * @sync: update after add_inbuf and/or add_outbuf + * vdev: the virtio_device we're talking about. + * inout: VIRTIO_IN and/or VIRTIO_OUT + * After one or more add_inbuf/add_outbuf calls, invoke this to kick + * the virtio layer. + * @get_outbuf: get the next used outbuf. + * vdev: the virtio_device we're talking about. + * len: the length written into the outbuf + * Returns NULL or the "data" token handed to add_outbuf (which has been + * detached). + * @get_inbuf: get the next used inbuf. + * vdev: the virtio_device we're talking about. + * len: the length read from the inbuf + * Returns NULL or the "data" token handed to add_inbuf (which has been + * detached). + * @detach_outbuf: make sure sent sg can no longer be read. + * vdev: the virtio_device we're talking about. + * id: the id returned from add_outbuf. + * This is usually used for shutdown. Don't try to detach twice. + * @detach_inbuf: make sure sent sg can no longer be written to. + * vdev: the virtio_device we're talking about. + * id: the id returned from add_inbuf. + * This is usually used for shutdown. Don't try to detach twice. + * @restart_in: restart calls to driver_ops->in after it returned false. + * vdev: the virtio_device we're talking about. + * This returns "false" (and doesn't re-enable) if there are pending + * inbufs, to avoid a race. + * @restart_out: restart calls to driver_ops->out after it returned false. + * vdev: the virtio_device we're talking about. + * This returns "false" (and doesn't re-enable) if there are pending + * outbufs, to avoid a race. + * + * Locking rules are straightforward: the driver is responsible for + * locking. Outbuf operations can be called in parallel to inbuf + * operations, but no two outbuf operations nor two inbuf operations + * may be invoked simultaneously. + * + * All operations can be called in any context. + */ +struct virtio_ops { + unsigned long (*add_outbuf)(struct virtio_device *vdev, + const struct scatterlist sg[], + unsigned int num, + void *data); + + unsigned long (*add_inbuf)(struct virtio_device *vdev, + struct scatterlist sg[], + unsigned int num, + void *data); + + void (*sync)(struct virtio_device *vdev, enum virtio_dir inout); + + void *(*get_outbuf)(struct virtio_device *vdev, unsigned int *len); + void *(*get_inbuf)(struct virtio_device *vdev, unsigned int *len); + + void (*detach_outbuf)(struct virtio_device *vdev, unsigned long id); + void (*detach_inbuf)(struct virtio_device *vdev, unsigned long id); + + bool (*restart_in)(struct virtio_device *vdev); + bool (*restart_out)(struct virtio_device *vdev); +}; +#endif /* _LINUX_VIRTIO_H */ _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization