Re: [kvm-devel] [PATCH RFC 1/3] virtio infrastructure

Rusty Russell wrote:

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 detach input and output buffers; as the
buffers are used up their associated "used" pointers are filled in.

  

Good stuff.

+/**
+ * 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.
+ *	used: the length sent (set once sending is done).
+ *      Returns an identifier 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.
+ *	used: the length sent (set once data received).
+ *      Returns an identifier or an error (eg. -ENOSPC).
  

Instead of 'used', how about a completion callback (with associated data
pointer)?  A new helper, virtio_complete(), would call the callback for
all completed requests.  It would eliminate all the tedious scanning
used to match the identifier.

It would also be nice to support a bit of non-buffer data, like a set of
bitflags.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.