[PATCH 2/6] KVM: PPC: Book3E: Refactor SPE/FP exit handling

[Alexander Graf]

On 03.07.2013, at 15:53, Caraman Mihai Claudiu-B02008 wrote:

>>> -#ifdef CONFIG_SPE
>>> 	case BOOKE_INTERRUPT_SPE_ALTIVEC_UNAVAIL: {
>>> -		if (vcpu->arch.shared->msr & MSR_SPE)
>>> -			kvmppc_vcpu_enable_spe(vcpu);
>>> -		else
>>> -			kvmppc_booke_queue_irqprio(vcpu,
>>> -
>> BOOKE_IRQPRIO_SPE_ALTIVEC_UNAVAIL);
>>> +		if (kvmppc_supports_spe()) {
>>> +			bool enabled = false;
>>> +
>>> +#ifndef CONFIG_KVM_BOOKE_HV
>>> +			if (vcpu->arch.shared->msr & MSR_SPE) {
>>> +				kvmppc_vcpu_enable_spe(vcpu);
>>> +				enabled = true;
>>> +			}
>>> +#endif
>> 
>> Why the #ifdef? On HV capable systems kvmppc_supports_spe() will just
>> always return false. 
> 
> AltiVec and SPE unavailable exceptions follows the same path. While 
> kvmppc_supports_spe() will always return false kvmppc_supports_altivec()
> may not.

There is no chip that supports SPE and HV at the same time. So we'll never hit this anyway, since kvmppc_supports_spe() always returns false on HV capable systems.

Just add a comment saying so and remove the ifdef :).


Alex

> 
>> And I don't really understand why HV would be special in the first place
>> here. Is it because we're accessing shared->msr?
> 
> You are right on HV case MSP[SPV] should be always zero when an unavailabe
> exception take place. The distrinction was made because on non HV the guest
> doesn't have direct access to MSR[SPE]. The name of the bit (not the position)
> was changed on HV cores.
> 
>> 
>>> +			if (!enabled)
>>> +				kvmppc_booke_queue_irqprio(vcpu,
>>> +					BOOKE_IRQPRIO_SPE_ALTIVEC_UNAVAIL);
>>> +		} else {
>>> +			/*
>>> +			 * Guest wants SPE, but host kernel doesn't support it.
>> 
>> host kernel or hardware
> 
> Ok.
> 
> -Mike
>