Required backwards support level?

[Lauri Kasanen]

Hi,

Obviously old userspace + new kernel combo needs to be supported. But
I'm not so sure about a mixed case, does old userspace + new userspace
need to be supported to run at the same time?

For example, a new 64-bit mesa+libdrm and a 32-bit old set, both
running apps at the same time.

Or is it acceptable to assume that once a new userspace has been run,
an old one won't be run for this boot?

- Lauri