Re: [PATCH AUTOSEL 5.19 05/58] arm64: kernel: drop unnecessary PoC cache clean+invalidate

[Sasha Levin]

On Mon, Aug 08, 2022 at 11:05:29AM +0200, Ard Biesheuvel wrote:
> On Mon, 8 Aug 2022 at 03:31, Sasha Levin <sashal@xxxxxxxxxx> wrote:
> > From: Ard Biesheuvel <ardb@xxxxxxxxxx>
> >
> > [ Upstream commit 2e945851e26836c0f2d34be3763ddf55870e49fe ]
> >
> > Some early boot code runs before the virtual placement of the kernel is
> > finalized, and we used to go back to the very start and recreate the ID
> > map along with the page tables describing the virtual kernel mapping,
> > and this involved setting some global variables with the caches off.
> >
> > In order to ensure that global state created by the KASLR code is not
> > corrupted by the cache invalidation that occurs in that case, we needed
> > to clean those global variables to the PoC explicitly.
> >
> > This is no longer needed now that the ID map is created only once (and
> > the associated global variable updates are no longer repeated). So drop
> > the cache maintenance that is no longer necessary.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> > Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> > Link: https://lore.kernel.org/r/20220624150651.1358849-9-ardb@xxxxxxxxxx
> > Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
>
> NAK
>
> This patch *must* *not* be backported. It will break the boot.

Appologies for this one, this was a technical issue on my end and I owe
a beer for yourself and few other folks that should have been filtered
out.

I'll drop all your patches from the AUTOSEL queue.

--
Thanks,
Sasha