Re: [PATCH 00/45] arm Spectre fix backport review for LTS 4.9

[Ivaylo Dimitrov]

Hi,

On  8.03.2018 15:21, Pali RohÃr wrote:
> On Thursday 08 March 2018 13:27:15 Pavel Machek wrote:
> > Hi!
> >
> > > Resent without non-upstream patches.
> > >
> > > This backport patchset fixed the spectre issue, it's original branch:
> > > https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=kpti
> > > A few dependency or fixingpatches are also picked up, if they are necessary
> > >   and no functional changes.
> > >
> > > No bug found from kernelci.org and lkft testing. It also could be gotten from:
> > >
> > > git://git.linaro.org/kernel/linux-linaro-stable.git v4.9-spectre-upstream-only
> > >
> > > Comments are appreciated!
> >
> > Not entirely related to this patched, but... I have few older ARM
> > boards here, and Nokia N9000 I really care about.
> >
> > AFAICT Meltdown is arm64 only?
>
> IIRC ARMv7 is not affected by meltdown.
>
> > Spectre affects the older boards, too, right? Was there any work done
> > on that? cpuinfo says "ARMv7" for N900.
>
> I remember that I saw some spectre patches for ARMv7 on LKML.
>
> In general for ARMv7 it is problematic as mitigation needs to change IBE
> bit which is not possible on OMAP HS devices. But for Nokia N900 there
> is special code which do it via smc instruction (function
> rx51_secure_update_aux_cr(), see also nokia_n900_legacy_init()).

I *think* N900 should be safe from spectre attack as a side effect of 
thumb2 errata (430973) workaround (BTB is flushed on every context 
switch), but don't quote me on that one, lets more knowledgeable than me 
to confirm first.

Ivo