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

Excerpts from Daniel Axtens's message of February 26, 2021 4:06 pm:

Hi Nick,

quoted

 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 <redacted>

Thanks,
Nick