Re: [Qemu-devel] [PATCH 3/3] scsi-disk: Deprecate device_id fallback to BlockBackend name

[Daniel P . Berrangé]

On Fri, Jan 25, 2019 at 06:46:53PM +0100, Kevin Wolf wrote:
> We should never have exposed BlockBackend names to the guest, it's a
> host detail. Deprecate this behaviour. Users who need to maintain the
> guest ABI can explicitly set the value with the device_id property.

I don't think we've deprecated things in the past which would cause
a guest ABI change when finally deleted.

Shouldn't we be instead setting using machine type versioning here,
so that existing machine types keep using the blk_name() fallback
forever, while QEMU 4.0+ machine types avoid blk_name() fallback
immediately.

> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>  hw/scsi/scsi-disk.c  |  5 +++++
>  qemu-deprecated.texi | 22 +++++++++++++++++++++-
>  2 files changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
> index e74e1e7c48..38f1fe2570 100644
> --- a/hw/scsi/scsi-disk.c
> +++ b/hw/scsi/scsi-disk.c
> @@ -2366,6 +2366,11 @@ static void scsi_realize(SCSIDevice *dev, Error **errp)
>              const char *str = blk_name(s->qdev.conf.blk);
>              if (str && *str) {
>                  s->device_id = g_strdup(str);
> +                warn_report("Using the backend drive ID for the Device "
> +                            "Identification VPD page is deprecated. "
> +                            "Please specify the serial or device_id options "
> +                            "explicitly to avoid guest-visible changes in "
> +                            "future QEMU versions.");
>              }
>          }
>      }

Regards,
Daniel
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