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

[Paolo Bonzini <pbonzini@redhat.com>]

Il 23/05/2013 08:17, Peter Lieven ha scritto:
> On 22.05.2013 23:55, Paolo Bonzini wrote:
>> 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.
> 
> I can just report, that I have used the patch that does it that way and
> it works.

What do you mean by "that way"? :)

Paolo

> Maybe Windows is calculating the uptime by the reference counter?
> 
> Peter
>