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SubjectRe: [PATCH 0/5] x86: another attempt at x86 pagetable unification

* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> > found a couple of bugs.
> >
> > firstly, 64-bit wasnt so lucky, you broke
> > iounmap()/change_page_attr()
> > :-)
>
> Crap. Worked for me. I'll look into it.

well, there's an easy solution for unification patches: the resulting
object files must have _exactly the same_ content as without the
unification patches. (Modulo strings as WARN_ON()s referring to
include-file names.)

If they differ then the unification did something wrong. With your
patchset and the config i sent, the difference is visible in the image
size already:

text data bss dec hex filename
7763766 967330 5812328 14543424 ddea40 vmlinux.after
7763811 967330 5812328 14543469 ddea6d vmlinux.before

also, reducing the size and scope of changes helps as well - because
that way it can be bisected down to specific changes. Mistakes
inevitably happen, especially if you do not enforce a rigid
byte-for-byte correctness along the way. You did 5 rather large patches,
and it's not testable because your unification steps were too coarse.

In other words: you were asking for trouble and you got it :-)

Ingo


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