[Qemu-devel] [PATCH 0/2] Add serial number support for virtio_blk

[john cooper <john.cooper@third-harmonic.com>]

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[Repost -- neglected to add qemu-devel in my
prior post.]

This patch allows passing of a virtio_blk drive
serial number from qemu into a guest's virtio_blk
driver, and provides a means to access the serial
number from a guest's userspace.

Equivalent functionality currently exists for IDE
and SCSI, however it is not yet implemented for
virtio.  Scenarios exist where guest code relies
on a unique drive serial number to correctly
identify the machine environment in which it
exists.

The following two patches implement the above

     qemu-vblk-serial.patch

which provides the qemu missing bits to interpret
a '-drive .. serial=XYZ ..' flag, and

     virtio_blk-serial.patch

which extracts this information and makes it
available to guest userspace via ioctl.

Attached to this patch header is a trivial example
program which retrieves the serial number from
guest userspace.

The above patches are relative to kvm-84 and
2.6.28 respectively.

-john


-- 
john.cooper@third-harmonic.com

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/* example: retrieve serial number from virtio block device
 */
#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
#include <linux/virtio_blk.h>

#define iswhite(c)	(!('!' <= (c) && (c) <= '~'))

#ifndef VBLK_GET_SN
#define VBLK_GET_SN ((unsigned int)('V' << 24 | 'B' << 16 | 'L' << 8 | 'K'))
#endif

/* get virtblk drive serial#
 */
int main(int ac, char ***av)
{
	int fd, nb, i;
	unsigned char sn[30];
	unsigned char *p;

	sn[0] = sizeof (sn);
	if ((fd = open("/dev/vda", O_RDONLY)) < 0)
		perror("can't open device"), exit(1);
	else if ((nb = ioctl(fd, VBLK_GET_SN, &sn)) < 0)
		perror("can't ioctl device"), exit(1);
	printf("returned %d bytes:\n", nb);
	for (p = sn, i = nb; 0 <= --i; ++p)
		printf("%02x%c", *p, i ? ' ' : '\t');
	for (p = sn, i = nb; 0 <= --i; ++p)
		printf("%c%s", iswhite(*p) ? '.' : *p, i ? "" : "\n");
	return (0);
}