Re: [Qemu-devel] cross version compatibility and qemu version

[Peter Maydell]

On 4 August 2013 11:20, Michael S. Tsirkin <address@hidden> wrote:
> I was looking at cross-version migration issues, in the
> hope that we can fix most of them for release 1.6.
> I noticed that we still use QEMU_VERSION in hardware.

We fixed most of these back in 2012, but I guess one or
two slipped through the net.

> hw/scsi/megasas.c:    snprintf(info.package_version, 0x60, "%s-QEMU", 
> QEMU_VERSION);
> hw/usb/redirect.c:#define VERSION "qemu usb-redir guest " QEMU_VERSION
>
> These look like a bug that will break cross version
> compatibility - I think need to change both instances
> to qemu_get_version()?

The USB one is OK, as the version string is only passed
to the usbredir-host for debugging purposes and isn't
visible to the guest. See this patch which reverted a
change which made it use qemu_get_version():

http://lists.gnu.org/archive/html/qemu-devel/2012-09/msg01903.html

> megasas also includes the build date/time of QEMU - this
> clearly removed any hope to be exactly compatible.
> I'm not sure what to do with respect to this:
> let's stop the clock at an arbitrary date?
> Add property for management to control this as well?

I would go for using an arbitrary (and preferably
obviously wrong) date, or just dropping the fields
altogether if the hardware format permits (it probably
doesn't).

-- PMM