Re: [kvm-devel] [PATCH 2/3] kvmclock - the host part.

[Izik Eidus <izike@qumranet.com>]

Glauber de Oliveira Costa wrote:
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> Dong, Eddie escreveu:
>   
> > > +static void kvm_write_guest_time(struct kvm_vcpu *vcpu) +{
> > > +	struct timespec ts;
> > > +	int r;
> > > +
> > > +	if (!vcpu->clock_gpa)
> > > +		return;
> > > +
> > > +	/* Updates version to the next odd number, indicating
> > > we're writing */
> > > +	vcpu->hv_clock.version++;
> > > +	kvm_write_guest(vcpu->kvm, vcpu->clock_gpa,
> > > &vcpu->hv_clock, PAGE_SIZE);
> > > +
> > > +	kvm_get_msr(vcpu, MSR_IA32_TIME_STAMP_COUNTER,
> > > +			  &vcpu->hv_clock.last_tsc);
> > > +
> > > +	ktime_get_ts(&ts);
> > >       
> > Do we need to disable preemption here?
> >     
> After thinking for a little while, you are theoretically right.
> In the current state, we could even be preempted between all operations
> ;-) Maybe after avi's suggestion of moving the call to it it will end up
> in a preempt safe region, but anyway, it's safer to add the preempt
> markers here.
> I'll put it in next version, thanks
>   
note that you cant call to kvm_write_guest with preemption disabled 
(witch you do few lines below)
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