Re: [PATCH RFC 3/3] virtio infrastructure: example block driver

[Carsten Otte <cotte-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>]

Rusty Russell wrote:
> Example block driver using virtio.
> 
> The block driver uses outbufs with sg[0] being the request information
> (struct virtio_blk_outhdr) with the type, sector and inbuf id.  For a
> write, the rest of the sg will contain the data to be written.
> 
> The first segment of the inbuf is a result code (struct
> virtio_blk_inhdr).  For a read, the rest of the sg points to the input
> buffer.
> 
> TODO:
> 	1) Ordered tag support.
Implementing a do_request function has quite a few disadvantages over 
hooking into q->make_request_fn. This way, we have the device plug 
(latency), request merging, and I/O scheduling inside the guest.
It seems preferable to do that in the host, especially when requests 
of multiple guests end up on the same physical media (shared access, 
or partitioned).

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