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

[Peter Lieven <pl@dlhnet.de>]

On 23.05.2013 11:54, Paolo Bonzini wrote:
> 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"? :)

Ups sorry… I meant the way it was implemented in the old patch (I sent a few days ago).

@@ -1426,6 +1428,21 @@ static int set_msr_hyperv_pw(struct kvm_
		if (__copy_to_user((void   *)addr, instructions, 4))
			return 1;
		kvm->arch.hv_hypercall = data;
+		kvm->arch.hv_ref_count = get_kernel_ns();
+ 		break;
+	}
+	case HV_X64_MSR_REFERENCE_TSC: {
+		u64 gfn;
+		unsigned long addr;
+		u32 hv_tsc_sequence;
+		gfn = data >> HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT;
+		addr = gfn_to_hva(kvm, gfn);
+		if (kvm_is_error_hva(addr))
+			return 1;
+		hv_tsc_sequence = 0x0; //invalid
+		if (__copy_to_user((void   *)addr, (void __user *) &hv_tsc_sequence, sizeof(hv_tsc_sequence)))
+			return 1;		
+		kvm->arch.hv_reference_tsc = data;
		break;
	}
	default:
@@ -1826,6 +1843,17 @@ static int get_msr_hyperv_pw(struct kvm_
	case HV_X64_MSR_HYPERCALL:
		data = kvm->arch.hv_hypercall;
		break;
+	case HV_X64_MSR_TIME_REF_COUNT: {
+		u64 now_ns;
+		local_irq_disable();
+		now_ns = get_kernel_ns();
+		data = div_u64(now_ns + kvm->arch.kvmclock_offset - kvm->arch.hv_ref_count,100);
+		local_irq_enable();
+		break;
+	}
+	case HV_X64_MSR_REFERENCE_TSC:
+		data = kvm->arch.hv_reference_tsc;
+		break;
	default:
		pr_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
		return 1;


Peter