Re: [PATCH v3 12/16] KVM: Move x86's perf guest info callbacks to generic KVM

[Sean Christopherson]

On Mon, Oct 11, 2021, Marc Zyngier wrote:
> On Wed, 22 Sep 2021 01:05:29 +0100, Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > index ed940aec89e0..828b6eaa2c56 100644
> > --- a/arch/arm64/include/asm/kvm_host.h
> > +++ b/arch/arm64/include/asm/kvm_host.h
> > @@ -673,6 +673,14 @@ int io_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa);
> >  void kvm_perf_init(void);
> >  void kvm_perf_teardown(void);
> >  
> > +#ifdef CONFIG_GUEST_PERF_EVENTS
> > +static inline bool kvm_arch_pmi_in_guest(struct kvm_vcpu *vcpu)
> 
> Pardon my x86 ignorance, what is PMI? PMU Interrupt?

Ya, Performance Monitoring Interrupt.  I didn't realize the term wasn't common
perf terminology.  Maybe kvm_arch_perf_events_in_guest() to be less x86-centric?

> > +{
> > +	/* Any callback while a vCPU is loaded is considered to be in guest. */
> > +	return !!vcpu;
> > +}
> > +#endif
> 
> Do you really need this #ifdef?

Nope, should compile fine without it, though simply dropping the #ifdef would make
make the semantics of the function wrong, even if nothing consumes it.  Tweak it
to use IS_ENABLED()?

	return IS_ENABLED(CONFIG_GUEST_PERF_EVENTS) && !!vcpu;