Re: CONFIG_XEN_COMPAT_030002 broken?

["Jan Beulich" <jbeulich@novell.com>]

>Also, is it necessary to default to 3.0.2 behaviour? Could we have
>kernel_page_user==0 initially and then change the value only if 3.0.2 is
>detected? This would provide a sanity check that check_page_user_flag() is
>being executed early enough. We could even set kernel_page_user to a garbage
>value initially, like ~0.

I think it's better the way Gerd had it (my patch also does it that way) - adding
extra _PAGE_USER when not needed is not wrong afaics, only hurts performance,
whereas missing to add it when needed would crash the kernel. While that might
help verify that the check is done early enough, it doesn't guarantee anything
since certain code paths may not be taken, and so we may enjoy false safety.

Jan