Re: [RFC PATCH v2 1/2] add support for Hyper-V reference time counter

[Gleb Natapov <gleb@redhat.com>]

On Wed, May 22, 2013 at 12:32:57AM -0300, Marcelo Tosatti wrote:
> On Wed, May 22, 2013 at 06:28:47AM +0300, Gleb Natapov wrote
> > > > +	case HV_X64_MSR_TIME_REF_COUNT:
> > > >  		r = true;
> > > >  		break;
> > > >  	}
> > > > @@ -1827,6 +1829,29 @@ static int set_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> > > >  		if (__copy_to_user((void __user *)addr, instructions, 4))
> > > >  			return 1;
> > > >  		kvm->arch.hv_hypercall = data;
> > > > +		local_irq_disable();
> > > > +		kvm->arch.hv_ref_count = get_kernel_ns();
> > > > +		local_irq_enable();
> > > > +		break;
> > > 
> > > local_irq_disable/local_irq_enable not needed.
> > >
> > get_kernel_ns has WARN_ON(preemptible()) so at least preempt_disable()
> > is needed, but all callers of the function disable interrupts.
> 
> OK. Its not necessary to disable interrupts (this is a left over of
> kvm_guest_update_time).
So preempt_disable() then? Should we change other callers?

--
			Gleb.