[U-Boot] U-Boot, cache speculation side channel attacks and ARM

[Marc Zyngier]

On Sat, 20 Jan 2018 11:45:08 +0100
Michael Nazzareno Trimarchi <michael at amarulasolutions.com> wrote:

> Hi Marc
> 
> On Sat, Jan 20, 2018 at 11:42 AM, Marc Zyngier <marc.zyngier at arm.com> wrote:
> > On Fri, 19 Jan 2018 16:56:14 -0500
> > Tom Rini <trini at konsulko.com> wrote:
> >  
> >> Hey all,
> >>
> >> So, now that things have quieted down a little bit in this area, I've
> >> been wondering about something.  Over on the U-Boot side of things, are
> >> there changes we need to make in order to support the kernel side of the
> >> various mitigations properly?  I know that for example currently
> >> https://developer.arm.com/support/security-update talks about ATF
> >> patches, in the context of AArch64 however.  But on the other hand for
> >> variant 2, there's nothing listed on the Linux side for 32bit ARM, but
> >> there is for non-Linux OSes.
> >>
> >> And, in the event I'm also missing something else entirely that we need
> >> to do here, is there something that we need to be doing?  Or is it still
> >> too early at this point in time to know?  
> >
> > I've so far posted two revisions of a small patch series that deals
> > with variant-2 on the affected 32bit Cortex-A cores. These patches are
> > currently stashed on the branch[1] pointed at by the web page you
> > mentioned.
> >
> > A prerequisite for Cortex-A8 and A15 is that ACTLR[0] (IBE) is set from
> > secure mode. Cortex-A12/A17 do not need this.  
> 
> So IBE is not a pre-requisite for Cortex A9 family. Is this correct?

Indeed. I'm not even sure A9 has that bit at all (ACTLR is
implementation specific). BPIALL works on A9 without any other setting.

> I have already back--ported those patches on kernel 3.4. Is those enough?

Define enough. These patches allow these CPUs to cope with variant-2,
and only variant-2. Variant-1 is still work in progress across all
architectures, variant-3 (aka Meltdown) doesn't concern 32bit ARM
implementations, and only A15 is susceptible to variant-3a.

Thanks,

	M.
-- 
Without deviation from the norm, progress is not possible.