"Michael S. Tsirkin" <m...@redhat.com> writes: > On Wed, Apr 13, 2016 at 06:17:29PM +0200, Markus Armbruster wrote: >> "Michael S. Tsirkin" <m...@redhat.com> writes: >> >> > On Wed, Apr 13, 2016 at 10:59:35AM +0200, Markus Armbruster wrote: >> >> I have a hard time coming up with realistic unclean breakage. >> > >> > The issue is that Linux is now exposing fw cfg to userspace. >> > So it's use is about to expand significantly. >> > >> > This is what I am trying to prevent: >> > - in 2016, users build a guest using a path XXX outside opt. >> > there's a warning on host, but it is not noticed. >> >> Amend: >> >> The guest treats path XXX as optional. >> >> > - in 2020, qemu starts using path XXX for internal purposes. >> > - using guest from 2016 now breaks uncleanly on this new qemu >> >> Amend: >> >> when we're not specifying the optional path XXX with -fw_cfg. >> >> > since guest thinks it's talking to the external tool. >> >> Okay, that's a much more plausible scenario. The question remains >> whether preventing it justifies the compat break and the additional >> interface complexity. > > there is no break as long as people follow the rules.
-fw_cfg exists since 2.4. You can't slap rules onto it in 2.6, and immediately claim compatibility matters only for usage following these rules.
