[Qemu-devel] [PATCH 0/2] Add serial number support for virtio_blk, V2

[john cooper]

[Resend of earlier patch: 1/2 rebased to qemu-kvm,
2/2 minor tweak]

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-2.patch

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

   virtio_blk-serial-2.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 qemu-kvm.git and
2.6.29.3 respectively.

-john

--
address@hidden

/* 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);
}