[PATCH v2 05/37] KVM: PPC: Book3S HV: Ensure MSR[ME] is always set in guest MSR

[Nicholas Piggin]

Excerpts from Daniel Axtens's message of February 26, 2021 4:06 pm:
> Hi Nick,
> 
>>  void kvmppc_set_msr_hv(struct kvm_vcpu *vcpu, u64 msr)
>>  {
>> +	/*
>> +	 * Guest must always run with machine check interrupt
>> +	 * enabled.
>> +	 */
>> +	if (!(msr & MSR_ME))
>> +		msr |= MSR_ME;
> 
> This 'if' is technically redundant but you mention a future patch warning
> on !(msr & MSR_ME) so I'm holding off on any judgement about the 'if' until
> I get to that patch :)

That's true. The warning is actually further down when we're setting up 
the msr to run in guest mode. At this point the MSR I think comes from
qemu (and arguably the guest setup code shouldn't need to know about HV
specific MSR bits) so a warning here wouldn't be appropriate.

I could remove the if, although the compiler might already do that.

> 
> The patch seems sane to me, I agree that we don't want guests running with
> MSR_ME=0 and kvmppc_set_msr_hv already ensures that the transactional state is
> sane so this is another sanity-enforcement in the same sort of vein.
> 
> All up:
> Reviewed-by: Daniel Axtens <dja at axtens.net>

Thanks,
Nick