On 20/12/12 12:22, Peter De Schrijver wrote:
>>>>> +
>>>>> + /* CNTFRQ */
>>>>> + asm("mcr p15, 0, %0, c14, c0, 0\n" : : "r" (freq));
>>>>> + asm("mrc p15, 0, %0, c14, c0, 0\n" : "=r" (val));
>>>>> + BUG_ON(val != freq);
>>>>
>>>> This is scary. CNTFRQ is only writable from secure mode, and will
>>>> explode in any other situation.
>>>>
>>>> Also, writing to CNTFRQ doesn't change the timer frequency! This is just
>>>> a way for secure mode to tell the rest of the world the frequency the
>>>> timer is ticking at. Unless you've wired the input clock to be able to
>>>> change the frequency?
>>>
>>> ATM, our upstream kernel is expected in secure mode. This situation
>>> may be changed later, though....
>>
>> I appreciate this. But I expect this kernel to be also used on the
>> non-secure side if someone tried to run KVM with it. And this would go
>> bang right away.
>>
>
> But the guest wouldn't necessarily have this peripheral, or any other Tegra114
> peripheral for that matter?
The problem is not so much the guest but the host. The host has to be
booted in non-secure, so just saying "we do not support non-secure" is
not a very convincing argument.
Unless of course you've already decided that you don't want to support
KVM on this SoC...
M.
--
Jazz is not dead. It just smells funny...
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