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SubjectRe: [PATCH RFC v1 3/3] ARM hibernation / suspend-to-disk
On Sat, Feb 22, 2014 at 10:16:55AM +0000, Russell King - ARM Linux wrote:
> On Thu, Feb 20, 2014 at 04:27:55PM +0000, Lorenzo Pieralisi wrote:
> > I still do not understand why switching to idmap, which is a clone of
> > init_mm + 1:1 kernel mappings is required here. Why idmap ?
> >
> > And while at it, can't the idmap be overwritten _while_ copying back the
> > resume kernel ? Is it safe to use idmap page tables while copying ?
> >
> > I had a look at x86 and there idmap page tables used to resume are created
> > on the fly using safe pages, on ARM idmap is created at boot.
>
> That's fine.
>
> Remember, you're required to boot exactly the same kernel image when
> resuming as the kernel which created the suspend image. Unless you
> have random allocations going on, you should get the same layout for
> the idmap stuff at each boot.

Thanks Russell, now that's clear. We do need a copy of page tables
that are not tampered with while copying, and idmap works well for
that.

Lorenzo



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