Re: [PATCH RFC V3 2/3] kvm: Note down when cpu relax interceptedor pause loop exited

[Raghavendra K T]

On 07/13/2012 01:32 AM, Christian Borntraeger wrote:
> On 12/07/12 21:18, Raghavendra K T wrote:
> > +#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
> [...]
> > +	struct {
> > +		bool cpu_relax_intercepted;
> > +		bool dy_eligible;
> > +	} ple;
> > +#endif
> [...]
> >   	}
> >   	vcpu->run = page_address(page);
> > +	vcpu->ple.cpu_relax_intercepted = false;
> > +	vcpu->ple.dy_eligible = false;
>
> This struct is only defined if CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT is set, but here it
> is always accessed. Will break on !x86&&  !s390.

Yes! I forgot about archs in init function.
How about having
#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
vcpu->ple.cpu_relax_intercepted = false;
vcpu->ple.dy_eligible = false;
#endif

This would solve all the problem.

> >   	r = kvm_arch_vcpu_init(vcpu);
> >   	if (r<  0)
> > @@ -1577,6 +1579,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> >   	int pass;
> >   	int i;
> >
> > +	me->ple.cpu_relax_intercepted = true;
>
> dito

currently vcpu_on_spin is used only by x86 and s390. so if some other
arch in future uses vcpu_on_spin, I believe they also have to enable
CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
what do you think?

otherwise we have to add hook everywhere
> >   	/*
> >   	 * We boost the priority of a VCPU that is runnable but not
> >   	 * currently running, because it got preempted by something
> > @@ -1602,6 +1605,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> >   			}
> >   		}
> >   	}
> > +	me->ple.cpu_relax_intercepted = false;
>
> again.
>
> maybe define static inline access functions in kvm_host.h that are no-ops
> if CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT is not set.

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