[PATCH] KVM: arm: reserve bit in KVM_REG_ARM encoding for secure/nonsecure

[Marc Zyngier]

On 06/03/18 16:56, Peter Maydell wrote:
> On 6 March 2018 at 16:43, Marc Zyngier <marc.zyngier at arm.com> wrote:
>> On 06/03/18 16:26, Peter Maydell wrote:
>>> +/* For KVM currently all guest registers are nonsecure, but we reserve a bit
>>> + * in the encoding to distinguish secure from nonsecure for banked registers.
>>> + */
>>
>> Nit:
>>
>> /*
>>  * This is the canonical comment style.
>>  */
>>
>> It might be worth pointing out in the comment that this only applies to
>> AArch32 system registers that are banked by security.
> 
> Sure. How about
> 
> /*
>  * For KVM currently all guest registers are nonsecure, but we reserve a bit
>  * in the encoding to distinguish secure from nonsecure for AArch32 system
>  * registers that are banked by security. This is 1 for the secure banked
>  * register, and 0 for the nonsecure banked register or if the register is
>  * not banked by security.
>  */
> 
> ?

Looks good to me.

> 
>>> +#define KVM_REG_ARM_SECURE_MASK      0x0000000010000000
>>> +#define KVM_REG_ARM_SECURE_SHIFT     28
>>>
>>>  #define ARM_CP15_REG_SHIFT_MASK(x,n) \
>>>       (((x) << KVM_REG_ARM_ ## n ## _SHIFT) & KVM_REG_ARM_ ## n ## _MASK)
>>>
>>
>> Don't you also need to define it on the arm64 side?
> 
> I don't think so, because AArch64 registers aren't security banked
> (except for some GICv3 ones, which aren't set via GET/SET_ONE_REG.)
> Or is there a case I'm missing?

There is still the case of AArch32 guests on arm64, for which you'd need
to replicate the change to arch/arm64/include/uapi/asm/kvm.h. The two
architectures have different userspace APIs.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...