[U-Boot] [PATCH 4/9] ARM: non-sec: reset CNTVOFF to zero

Marc Zyngier
2013-11-26T14:46:22Z

On 26/11/13 14:41, Andre Przywara wrote:
> On 11/21/2013 09:59 AM, Marc Zyngier wrote:
>> Before switching to non-secure, make sure that CNTVOFF is set
>> to zero on all CPUs. Otherwise, kernel running in non-secure
>> without HYP enabled (hence using virtual timers) may observe
>> timers that are not synchronized, effectively seeing time
>> going backward...
>
> Under what circumstances would native Linux use the virtual timers? When
> VIRT_EXT is not defined?

Yes. In general, when the kernel is not entered in HYP mode.

M.

> Regards,
> Andre.
>
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>> arch/arm/cpu/armv7/nonsec_virt.S | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S
>> index 648066f..bbacbce 100644
>> --- a/arch/arm/cpu/armv7/nonsec_virt.S
>> +++ b/arch/arm/cpu/armv7/nonsec_virt.S
>> @@ -53,7 +53,14 @@ _secure_monitor:
>> mrceq p15, 0, r0, c12, c0, 1 @ get MVBAR value
>> mcreq p15, 4, r0, c12, c0, 0 @ write HVBAR
>> #endif
>> + bne 1f
>>
>> + @ Reset CNTVOFF to 0 before leaving monitor mode
>> + mrc p15, 0, r0, c0, c1, 1 @ read ID_PFR1
>> + ands r0, r0, #CPUID_ARM_GENTIMER_MASK @ test arch timer bits
>> + movne r0, #0
>> + mcrrne p15, 4, r0, r0, c14 @ Reset CNTVOFF to zero
>> +1:
>> movs pc, lr @ return to non-secure SVC
>>
>> _hyp_trap:
>>
>
>

--
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