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

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

[Dietmar Eggemann]

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

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

[Russell King - ARM Linux]

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.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 13.8Mbps down 630kbps up
According to speedtest.net: 13Mbps down 490kbps up

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

[Morten Rasmussen]

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?

As it is we have to change the default setting of this new option to
make the platform useable as those messages are flooding the console. I
see >40 messages per second.

Morten

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

[Russell King - ARM Linux]

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.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 13.8Mbps down 630kbps up
According to speedtest.net: 13Mbps down 490kbps up

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

[Russell King - ARM Linux]

[-- Attachment #1: Type: text/plain, Size: 1151 bytes --]

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.

An alternative would be to give the patches in the attachment a test.
They're not finished yet, so I haven't sent them out, but still worth
testing.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 13.8Mbps down 630kbps up
According to speedtest.net: 13Mbps down 490kbps up

[-- Attachment #2: bl.tar.xz --]
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Re: arm: v4.18-rc5 with cpuidle on TC2 (A7 boot) spectre v2 issue

[Morten Rasmussen]

On Thu, Jul 19, 2018 at 02:32:22PM +0100, Russell King - ARM Linux 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.
> 
> An alternative would be to give the patches in the attachment a test.
> They're not finished yet, so I haven't sent them out, but still worth
> testing.

Thanks for sharing. I can confirm that your patches do cure the flood of warnings.

TC2 booting on A7:

[    0.002922] CPU: Testing write buffer coherency: ok
[    0.003347] CPU0: thread -1, cpu 0, socket 1, mpidr 80000100
[    0.004022] Setting up static identity map for 0x80100000 - 0x80100060
[    0.004265] ARM CCI driver probed
[    0.004648] TC2 power management initialized
[    0.004930] Hierarchical SRCU implementation.
[    0.006956] smp: Bringing up secondary CPUs ...
[    0.008712] CPU1: thread -1, cpu 0, socket 0, mpidr 80000000
[    0.008720] CPU1: Spectre v2: firmware did not set auxiliary control register IBE bit, system vulnerable
[    0.009934] CPU2: thread -1, cpu 1, socket 0, mpidr 80000001
[    0.009940] CPU2: Spectre v2: firmware did not set auxiliary control register IBE bit, system vulnerable
[    0.011147] CPU3: thread -1, cpu 1, socket 1, mpidr 80000101
[    0.012350] CPU4: thread -1, cpu 2, socket 1, mpidr 80000102
[    0.012468] smp: Brought up 1 node, 5 CPUs
[    0.012490] SMP: Total of 5 processors activated (240.00 BogoMIPS).
[    0.012499] CPU: All CPU(s) started in SVC mode.

TC2 booting on A15:

[    0.002045] CPU0: Spectre v2: firmware did not set auxiliary control register IBE bit, system vulnerable
[    0.002311] CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
[    0.002809] Setting up static identity map for 0x80100000 - 0x80100060
[    0.003000] ARM CCI driver probed
[    0.003408] TC2 power management initialized
[    0.003637] Hierarchical SRCU implementation.
[    0.005177] smp: Bringing up secondary CPUs ...
[    0.006170] CPU1: thread -1, cpu 1, socket 0, mpidr 80000001
[    0.006176] CPU1: Spectre v2: firmware did not set auxiliary control register IBE bit, system vulnerable
[    0.008137] CPU2: thread -1, cpu 0, socket 1, mpidr 80000100
[    0.009304] CPU3: thread -1, cpu 1, socket 1, mpidr 80000101
[    0.010405] CPU4: thread -1, cpu 2, socket 1, mpidr 80000102
[    0.010537] smp: Brought up 1 node, 5 CPUs
[    0.010562] SMP: Total of 5 processors activated (240.00 BogoMIPS).
[    0.010572] CPU: All CPU(s) started in SVC mode.

No further warnings for either configuration.

For reference, this a partial output from later in the boot process when
booting on A7 with 4.18-rc5 _without_ your patches:

[    5.576176] device-mapper: ioctl: 4.39.0-ioctl (2018-04-03) initialised: dm-devel@redhat.com
[    5.601689] cpu cpu0: bL_cpufreq_init: CPU 0 initialized
[    5.618670] cpu cpu1: bL_cpufreq_init: CPU 1 initialized
[    5.635583] arm_big_little: bL_cpufreq_register: Registered platform driver: vexpress-spc
[    5.661112] mmci-pl18x 1c050000.mmci: Got CD GPIO
[    5.675235] mmci-pl18x 1c050000.mmci: Got WP GPIO
[    5.687783] CPU2: Spectre v2: incorrect context switching function, system vulnerable
[    5.689623] mmci-pl18x 1c050000.mmci: mmc0: PL180 manf 41 rev0 at 0x1c050000 irq 26,27 (pio)
[    5.713217] CPU1: Spectre v2: incorrect context switching function, system vulnerable
[    5.718044] CPU2: Spectre v2: incorrect context switching function, system vulnerable
[    5.727896] CPU2: Spectre v2: incorrect context switching function, system vulnerable