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 23:20 +0100, Peter Lieven wrote:
> Am 08.01.2014 21:08, schrieb Vadim Rozenfeld:
> > On Wed, 2014-01-08 at 15:54 +0100, Peter Lieven wrote:
> >> On 08.01.2014 13:12, Vadim Rozenfeld wrote:
> >>> 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.
> >>
> >> Can you use these parameters for testing:
> >>
> >> -cpu qemu64,hv_relaxed,hv_vapic,hv_spinlocks=4096,hv_refcnt
> >> -rtc base=localtime -vga std  -usb -usbdevice tablet -no-hpet
> > 
> > My settings are:
> > -cpu qemu64,
> > +x2apic,family=0xf,hv_vapic,hv_spinlocks=0xfff,hv_relaxed,hv_tsc -m 1G
> > -smp 4
> 
> do you also see the jump if you leave the hv_tsc out and just use hv_refcnt?

Yes, almost the same results. I will try to re-check it on a different
machine tomorrow.
Best regards,
Vadim.

> 
> Peter
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