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Re: [libvirt] [Qemu-devel] [PATCH 1/3] scsi-disk: Don't use empty string as device id



On 1/25/19 6:46 PM, Kevin Wolf wrote:
> scsi-disk includes in the Device Identification VPD page, depending on
> configuration amongst others, a vendor specific designator that consists
> either of the serial number if given or the BlockBackend name (which is
> a host detail that better shouldn't have been leaked to the guest, but
> now we have to maintain it for compatibility).
> 
> With anonymous BlockBackends, i.e. scsi-disk devices constructed with
> drive=<node-name>, and no serial number explicitly specified, this ends
> up as an empty string. If this happens to more than one disk, we have
> accidentally signalled to the OS that this is a multipath setup, which
> is obviously not what was intended.
> 
> Instead of using an empty string for the vendor specific designator,
> simply leave out that designator, which makes Linux detect such setups
> as separate disks again.
> 
> Signed-off-by: Kevin Wolf <kwolf redhat com>

Reviewed-by: Philippe Mathieu-Daudé <philmd redhat com>

> ---
>  hw/scsi/scsi-disk.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
> index 0e9027c8f3..93eef40b87 100644
> --- a/hw/scsi/scsi-disk.c
> +++ b/hw/scsi/scsi-disk.c
> @@ -652,12 +652,14 @@ static int scsi_disk_emulate_vpd_page(SCSIRequest *req, uint8_t *outbuf)
>          DPRINTF("Inquiry EVPD[Device identification] "
>                  "buffer size %zd\n", req->cmd.xfer);
>  
> -        outbuf[buflen++] = 0x2; /* ASCII */
> -        outbuf[buflen++] = 0;   /* not officially assigned */
> -        outbuf[buflen++] = 0;   /* reserved */
> -        outbuf[buflen++] = id_len; /* length of data following */
> -        memcpy(outbuf + buflen, str, id_len);
> -        buflen += id_len;
> +        if (id_len) {
> +            outbuf[buflen++] = 0x2; /* ASCII */
> +            outbuf[buflen++] = 0;   /* not officially assigned */
> +            outbuf[buflen++] = 0;   /* reserved */
> +            outbuf[buflen++] = id_len; /* length of data following */
> +            memcpy(outbuf + buflen, str, id_len);
> +            buflen += id_len;
> +        }
>  
>          if (s->qdev.wwn) {
>              outbuf[buflen++] = 0x1; /* Binary */
> 


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