Re: arm: v4.18-rc5 with cpuidle on TC2 (A7 boot) spectre v2 issue

Russell King - ARM Linux
2018-07-19T11:16:52Z

On Thu, Jul 19, 2018 at 11:39:19AM +0100, Morten Rasmussen wrote:
> On Thu, Jul 19, 2018 at 11:01:10AM +0100, Russell King - ARM Linux wrote:
> > On Thu, Jul 19, 2018 at 11:42:50AM +0200, Dietmar Eggemann wrote:
> > > Hi,
> > >
> > > running v4.18-rc5 (plus still missing "power: vexpress: fix corruption in
> > > notifier registration", otherwise I get this rcu_sched stall issue) on TC2
> > > (A7 boot) with vanilla multi_v7_defconfig plus
> > > CONFIG_ARM_BIG_LITTLE_CPUIDLE=y gives me continuous:
> > >
> > > ...
> > > CPUX: Spectre v2: incorrect context switching function, system vulnerable
> > > ...
> > >
> > > messages.
> > >
> > > Work around is to disable CONFIG_HARDEN_BRANCH_PREDICTOR.
> >
> > or disable big.Little if you want the hardening.
> >
> > The choices are currently either protection against Spectre or big.Little
> > support since the two are mutually exclusive at the moment.
>
> Would it be possible to make those message only appear once like they do
> when booting on A15?

Yes, it's possible. Feel free to send a patch, thanks.