Re: Boot failures with net-next after rebase to v4.17.0-rc1

From: Linus Torvalds
Date: Tue Apr 24 2018 - 16:04:31 EST

On Tue, Apr 24, 2018 at 12:54 PM, Jesper Dangaard Brouer
<brouer@xxxxxxxxxx> wrote:
> Hi all,
> I'm experiencing boot failures with net-next git-tree after it got
> rebased/merged with Linus'es tree at v4.17.0-rc1.

I suspect it's the global bit stuff that came in very late in the
merge window, and had been developed and tested for a while before,
but showed some problems under some configs.

The fix is currently in the x86/pti tree in -tip, see:

x86/pti: Fix boot problems from Global-bit setting

and I expect it will percolate upstream soon.

In the meantime, it would be good to verify that merging that x86/pti
branch fixes it for you?

There is another candidate for boot problems - do you happen to have
CONFIG_DEFERRED_STRUCT_PAGE_INIT enabled? That can under certain
circumstances get a percpu setup page fault because memory hadn't been
initialized sufficiently.

The fix there is to move the mm_init() call one step earlier in
init_main(): start_kernel() (to before trap_init()).

And if it's neither of the above, I think you'll need to help bisect it.