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

[Marc Zyngier]

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 at 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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