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

[Paolo Bonzini <pbonzini@redhat.com>]

Il 22/05/2013 09:32, Vadim Rozenfeld ha scritto:
>> > @@ -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.
> 
> 
> What is the reasoning behind reading this time value at msr write time?
> [VR] Windows writs this MSR only once, during HAL initialization.
> So, I decided to treat this call as a partition crate event.
> 

But is it expected by Windows that the reference count starts counting
up from 0 at partition creation time?  If you could just use
(get_kernel_ns() + kvm->arch.kvmclock_offset) / 100, it would also be
simpler for migration purposes.

Paolo