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

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Message-ID: <2abc6c11-2e8c-a4ea-6911-0f495d90ace6@arm.com>
Date:   Thu, 19 Jul 2018 11:42:50 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        Qais Yousef <Qais.Yousef@....com>, linux-kernel@...r.kernel.org
Subject: arm: v4.18-rc5 with cpuidle on TC2 (A7 boot) spectre v2 issue

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.

-- Dietmar