----- Original Message ----- From: "Peter Lieven" <pl@xxxxxxxxx> To: "Paolo Bonzini" <pbonzini@xxxxxxxxxx> Cc: "Vadim Rozenfeld" <vrozenfe@xxxxxxxxxx>, "Marcelo Tosatti" <mtosatti@xxxxxxxxxx>, kvm@xxxxxxxxxxxxxxx, gleb@xxxxxxxxxx, pl@xxxxxxx Sent: Thursday, May 23, 2013 4:17:57 PM Subject: Re: [RFC PATCH v2 1/2] add support for Hyper-V reference time counter 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. Maybe Windows is calculating the uptime by the reference counter? [VR] Windows use it (reference counters/iTSC/PMTimer/HPET) as a time-stamp source for (Ke)QueryPerformanceCounter function. Peter -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
