Re: [Qemu-devel] [PATCH 0/4] Add virtio disk identification support

[Ryan Harper <ryanh@us.ibm.com>]

* john cooper <john.cooper@redhat.com> [2010-03-25 00:45]:
> This series adds the minimal support to qemu and virtio_blk
> to support passing of a virtio_blk serial id string from qemu
> through the guest driver and to the guest userland.
> 
> This is derived in part from a patch set posted by Rusty some
> time ago, but has been minimized to remove support for prior
> versions which attempted to provide the same functionality via
> pci config/io space.  This version rather uses a virtio request
> as proposed in Rusty's example.
> 
> Also removed is the packaging of the serial/id string within
> the glorious bag of bits returned by the ATA_IDENTIFY command.
> Here we transfer only the 20 bytes of serial/id string from
> qemu to the guest userland.  In the proposed interface, this
> is made available by an ioctl() into the virtio_blk driver
> however other interfaces (eg: /sys) have also been proposed.
> A code snippet is attached below as an example of ioctl usage.
> 
> The resulting code is quite minimal and I believe it addresses
> all concerns raised in prior versions.
> 
> -john

I've applied the qemu and kernel side of this patch series and tested
this out using the sample code below.  I've also reworked this example
into a virtioblk_id tool to work with udev to generate /dev/disk/by-id
links; I'll be submitting a patch set to linux-hotplug with these
changes, (and update for path_id) and some udev rules to
persistent-storage script to autogenerate by-id and by-path symlinks for
virtio-blk devices.

I've also got a patch to apply ontop of the qemu patches to generate a
default serial number if one isn't specified (like we do for ide
devices).

Anthony, is this series in your queue yet?

Acked-by: Ryan Harper <ryanh@us.ibm.com>

> 
> 
> 
> #include <stdio.h>
> #include <strings.h>
> #include <sys/types.h>
> #include <fcntl.h>
> #include <linux/hdreg.h>
> 
> #define IOCTL_CMD	'VBID'
> 
> main()
> {
> 	int fd, rv;
> 	char buf[512];
> 
> 	bzero(buf, sizeof (buf));
> 	if ((fd = open("/dev/vda", O_RDONLY)) < 0)
> 		perror("open");
> 	else if (ioctl(fd, IOCTL_CMD, buf) < 0)
> 		perror("ioctl");
> 	else
> 		printf("[%s]\n", buf);
> }
> 
> -- 
> john.cooper@redhat.com
> 

-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh@us.ibm.com