Re: [RFC PATCH v3 1/2] add support for Hyper-V reference time counter

[Vadim Rozenfeld <vrozenfe@redhat.com>]

On Wed, 2014-01-08 at 12:48 +0100, Peter Lieven wrote:
> On 08.01.2014 11:44, Vadim Rozenfeld wrote:
> > On Wed, 2014-01-08 at 11:15 +0100, Peter Lieven wrote:
> >> On 08.01.2014 10:40, Vadim Rozenfeld wrote:
> >>> On Tue, 2014-01-07 at 18:52 +0100, Peter Lieven wrote:
> >>>> Am 07.01.2014 10:36, schrieb Vadim Rozenfeld:
> >>>>> On Thu, 2014-01-02 at 17:52 +0100, Peter Lieven wrote:
> >>>>>> Am 11.12.2013 19:59, schrieb Marcelo Tosatti:
> >>>>>>> On Wed, Dec 11, 2013 at 04:53:05PM -0200, Marcelo Tosatti wrote:
> >>>>>>>> On Sun, Dec 08, 2013 at 10:33:38PM +1100, Vadim Rozenfeld wrote:
> >>>>>>>>> Signed-off: Peter Lieven <pl@dlh.net>
> >>>>>>>>> Signed-off: Gleb Natapov <gleb@redhat.com>
> >>>>>>>>> Signed-off: Vadim Rozenfeld <vrozenfe@redhat.com>
> >>>>>>>>>
> >>>>>>>>> v1 -> v2
> >>>>>>>>> 1. mark TSC page dirty as suggested by
> >>>>>>>>>       Eric Northup <digitaleric@google.com> and Gleb
> >>>>>>>>> 2. disable local irq when calling get_kernel_ns,
> >>>>>>>>>       as it was done by Peter Lieven <pl@dlhnet.de>
> >>>>>>>>> 3. move check for TSC page enable from second patch
> >>>>>>>>>       to this one.
> >>>>>>>>>
> >>>>>>>>> ---
> >>>>>>>>>    arch/x86/include/asm/kvm_host.h    |  2 ++
> >>>>>>>>>    arch/x86/include/uapi/asm/hyperv.h | 13 +++++++++++++
> >>>>>>>>>    arch/x86/kvm/x86.c                 | 39 +++++++++++++++++++++++++++++++++++++-
> >>>>>>>>>    include/uapi/linux/kvm.h           |  1 +
> >>>>>>>>>    4 files changed, 54 insertions(+), 1 deletion(-)
> >>>>>>>>>
> >>>>>>>>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> >>>>>>>>> index ae5d783..2fd0753 100644
> >>>>>>>>> --- a/arch/x86/include/asm/kvm_host.h
> >>>>>>>>> +++ b/arch/x86/include/asm/kvm_host.h
> >>>>>>>>> @@ -605,6 +605,8 @@ struct kvm_arch {
> >>>>>>>>>    	/* fields used by HYPER-V emulation */
> >>>>>>>>>    	u64 hv_guest_os_id;
> >>>>>>>>>    	u64 hv_hypercall;
> >>>>>>>>> +	u64 hv_ref_count;
> >>>>>>>>> +	u64 hv_tsc_page;
> >>>>>>>>>
> >>>>>>>>>    	#ifdef CONFIG_KVM_MMU_AUDIT
> >>>>>>>>>    	int audit_point;
> >>>>>>>>> diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
> >>>>>>>>> index b8f1c01..462efe7 100644
> >>>>>>>>> --- a/arch/x86/include/uapi/asm/hyperv.h
> >>>>>>>>> +++ b/arch/x86/include/uapi/asm/hyperv.h
> >>>>>>>>> @@ -28,6 +28,9 @@
> >>>>>>>>>    /* Partition Reference Counter (HV_X64_MSR_TIME_REF_COUNT) available*/
> >>>>>>>>>    #define HV_X64_MSR_TIME_REF_COUNT_AVAILABLE	(1 << 1)
> >>>>>>>>>
> >>>>>>>>> +/* A partition's reference time stamp counter (TSC) page */
> >>>>>>>>> +#define HV_X64_MSR_REFERENCE_TSC		0x40000021
> >>>>>>>>> +
> >>>>>>>>>    /*
> >>>>>>>>>     * There is a single feature flag that signifies the presence of the MSR
> >>>>>>>>>     * that can be used to retrieve both the local APIC Timer frequency as
> >>>>>>>>> @@ -198,6 +201,9 @@
> >>>>>>>>>    #define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_MASK	\
> >>>>>>>>>    		(~((1ull << HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT) - 1))
> >>>>>>>>>
> >>>>>>>>> +#define HV_X64_MSR_TSC_REFERENCE_ENABLE		0x00000001
> >>>>>>>>> +#define HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT	12
> >>>>>>>>> +
> >>>>>>>>>    #define HV_PROCESSOR_POWER_STATE_C0		0
> >>>>>>>>>    #define HV_PROCESSOR_POWER_STATE_C1		1
> >>>>>>>>>    #define HV_PROCESSOR_POWER_STATE_C2		2
> >>>>>>>>> @@ -210,4 +216,11 @@
> >>>>>>>>>    #define HV_STATUS_INVALID_ALIGNMENT		4
> >>>>>>>>>    #define HV_STATUS_INSUFFICIENT_BUFFERS		19
> >>>>>>>>>
> >>>>>>>>> +typedef struct _HV_REFERENCE_TSC_PAGE {
> >>>>>>>>> +	__u32 tsc_sequence;
> >>>>>>>>> +	__u32 res1;
> >>>>>>>>> +	__u64 tsc_scale;
> >>>>>>>>> +	__s64 tsc_offset;
> >>>>>>>>> +} HV_REFERENCE_TSC_PAGE, *PHV_REFERENCE_TSC_PAGE;
> >>>>>>>>> +
> >>>>>>>>>    #endif
> >>>>>>>>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> >>>>>>>>> index 21ef1ba..5e4e495a 100644
> >>>>>>>>> --- a/arch/x86/kvm/x86.c
> >>>>>>>>> +++ b/arch/x86/kvm/x86.c
> >>>>>>>>> @@ -840,7 +840,7 @@ EXPORT_SYMBOL_GPL(kvm_rdpmc);
> >>>>>>>>>    static u32 msrs_to_save[] = {
> >>>>>>>>>    	MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
> >>>>>>>>>    	MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
> >>>>>>>>> -	HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
> >>>>>>>>> +	HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL, HV_X64_MSR_TIME_REF_COUNT,
> >>>>>>>>>    	HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
> >>>>>>>>>    	MSR_KVM_PV_EOI_EN,
> >>>>>>>>>    	MSR_IA32_SYSENTER_CS, MSR_IA32_SYSENTER_ESP, MSR_IA32_SYSENTER_EIP,
> >>>>>>>>> @@ -1826,6 +1826,8 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
> >>>>>>>>>    	switch (msr) {
> >>>>>>>>>    	case HV_X64_MSR_GUEST_OS_ID:
> >>>>>>>>>    	case HV_X64_MSR_HYPERCALL:
> >>>>>>>>> +	case HV_X64_MSR_REFERENCE_TSC:
> >>>>>>>>> +	case HV_X64_MSR_TIME_REF_COUNT:
> >>>>>>>>>    		r = true;
> >>>>>>>>>    		break;
> >>>>>>>>>    	}
> >>>>>>>>> @@ -1865,6 +1867,29 @@ 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() + kvm->arch.kvmclock_offset;
> >>>>>>>>> +		local_irq_enable();
> >>>>>>>>
> >>>>>>>> Where does the docs say that HV_X64_MSR_HYPERCALL is the where the clock
> >>>>>>>> starts counting?
> >>>>>>>>
> >>>>>>>> No need to store kvmclock_offset in hv_ref_count? (moreover
> >>>>>>>> the name is weird, better name would be "hv_ref_start_time".
> >>>>>>>
> >>>>>>> Just add kvmclock_offset when reading the values (otherwise you have a
> >>>>>>> "stale copy" of kvmclock_offset in hv_ref_count).
> >>>>>>>
> >>>>>>
> >>>>>> After some experiments I think we do no need kvm->arch.hv_ref_count at all.
> >>>>>>
> >>>>>> I was debugging some weird clockjump issues and I think the problem is that after live migration
> >>>>>> kvm->arch.hv_ref_count is initialized to 0. Depending on the uptime of the vServer when the
> >>>>>> hypercall was set up this can lead to series jumps.
> >>>>>>
> >>>>>> So I would suggest to completely drop kvm->arch.hv_ref_count.
> >>>>>>
> >>>>>> And use simply this in get_msr_hyperv_pw().
> >>>>>>
> >>>>>>           case HV_X64_MSR_TIME_REF_COUNT: {
> >>>>>>                   data = div_u64(get_kernel_ns() + kvm->arch.kvmclock_offset, 100);
> >>>>>>                   break;
> >>>>>>           }
> >>>>>>
> >>>>>
> >>>>> Agreed. It should work as long as we rely on kvmclock_offset.
> >>>>> Vadim.
> >>>>
> >>>> I think we can rely on kvmclock_offset. Had you had a chance to do further testing
> >>>> during the weekend?
> >>>
> >>> Yes, and still testing.
> >>>
> >>> There is still some inconsistency in the value returned by
> >>> QueryPerformanceCounter during migration.
> >>
> >> With my proposal?
> >>
> >
> > Right.
> > Please see below QTC vs. NTP time stamp
> > before and after migration:
> >
> > C:\timedrift\objchk_win7_x86\i386>timedrift.exe
> > quantum = 15
> > QPC     NTP     Delta
> > 1311    1307    4
> > 2621    2618    3
> > 3932    3931    1
> > .......
> > .......
> > 38018   38014   4
> > Unable to wait for NTP reply from the SNTP server, GetLastError returns
> > 7279088
> > 142210  40113   102097
> > 143458  41357   102101
> > .......
> > .......
> > 156500  54615   101885
> >
> > NTP time changed from  38014 to 40113 ((40113 - 38014) / 100 = 21 mSec)
> > while QPC jumped from  38018 to 142210 ((142210 - 38014) / 100 = 1042
> > mSec)
> 
> How long was the downtime when you migrated the vServer?
I use Win7-32 for testing.
> 
> I have done similar tests and have not seen this...
> Can you show the relevant parts of your patch. Remember I use the REFERENCE_COUTNER not iTSC.
Yes, I also test it for reference counter.

        case HV_X64_MSR_TIME_REF_COUNT: {
//              u64 now_ns;
//              local_irq_disable();
//              now_ns = get_kernel_ns() + kvm->arch.kvmclock_offset;
//              data = div_u64(now_ns - kvm->arch.hv_ref_count, 100);
//              local_irq_enable();
                data = div_u64(get_kernel_ns() +
kvm->arch.kvmclock_offset, 100);
                break;
        }


> 
> Peter
>