From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org
Cc: Sean Christopherson <seanjc@google.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH v2 6/4] selftests: kvm: Add basic Hyper-V clocksources tests
Date: Thu, 18 Mar 2021 15:52:25 +0100 [thread overview]
Message-ID: <8735ws7bva.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <1176f351-220d-003e-2cae-65f0b42c8f18@redhat.com>
Paolo Bonzini <pbonzini@redhat.com> writes:
> On 18/03/21 15:09, Vitaly Kuznetsov wrote:
>> +static inline void check_tsc_msr_tsc_page(struct ms_hyperv_tsc_page *tsc_page)
>> +{
>> + u64 r1, r2, t1, t2;
>> + s64 delta_ns;
>> +
>> + /* Compare TSC page clocksource with HV_X64_MSR_TIME_REF_COUNT */
>> + t1 = mul_u64_u64_shr64(rdtsc(), tsc_page->tsc_scale) + tsc_page->tsc_offset;
>> + r1 = rdmsr(HV_X64_MSR_TIME_REF_COUNT);
>> + nop_loop();
>> + t2 = mul_u64_u64_shr64(rdtsc(), tsc_page->tsc_scale) + tsc_page->tsc_offset;
>> + r2 = rdmsr(HV_X64_MSR_TIME_REF_COUNT);
>> +
>> + delta_ns = ((r2 - r1) - (t2 - t1)) * 100;
>> + if (delta_ns < 0)
>> + delta_ns = -delta_ns;
>> +
>> + /* 1% tolerance */
>> + GUEST_ASSERT(delta_ns * 100 < (t2 - t1) * 100);
>> +}
>> +
>
> I think you should also be able to check r1 and r2 individually, not
> just r1 and r2. Is that correct?
Right, we could've checked r1 == t1 and r2 == t2 actually (with some
tiny margin of course). Let me try that.
--
Vitaly
next prev parent reply other threads:[~2021-03-18 14:53 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 14:37 [PATCH v2 0/4] KVM: x86: hyper-v: TSC page fixes Vitaly Kuznetsov
2021-03-16 14:37 ` [PATCH v2 1/4] KVM: x86: hyper-v: Limit guest to writing zero to HV_X64_MSR_TSC_EMULATION_STATUS Vitaly Kuznetsov
2021-03-16 14:37 ` [PATCH v2 2/4] KVM: x86: hyper-v: Prevent using not-yet-updated TSC page by secondary CPUs Vitaly Kuznetsov
2021-03-18 17:02 ` Marcelo Tosatti
2021-03-18 18:04 ` Marcelo Tosatti
2021-03-18 18:05 ` Paolo Bonzini
2021-03-18 18:30 ` Marcelo Tosatti
2021-03-19 9:29 ` Vitaly Kuznetsov
2021-03-16 14:37 ` [PATCH v2 3/4] KVM: x86: hyper-v: Track Hyper-V TSC page status Vitaly Kuznetsov
2021-03-17 8:07 ` Paolo Bonzini
2021-03-17 11:19 ` [PATCH v2 5/4] KVM: x86: hyper-v: Briefly document enum hv_tsc_page_status Vitaly Kuznetsov
2021-03-16 14:37 ` [PATCH v2 4/4] KVM: x86: hyper-v: Don't touch TSC page values when guest opted for re-enlightenment Vitaly Kuznetsov
2021-03-18 14:09 ` [PATCH v2 6/4] selftests: kvm: Add basic Hyper-V clocksources tests Vitaly Kuznetsov
2021-03-18 14:26 ` Paolo Bonzini
2021-03-18 14:52 ` Vitaly Kuznetsov [this message]
2021-03-18 15:01 ` Paolo Bonzini
2021-03-18 15:23 ` Vitaly Kuznetsov
2021-03-18 15:27 ` Paolo Bonzini
2021-03-18 16:57 ` Marcelo Tosatti
2021-03-18 17:50 ` Paolo Bonzini
2021-03-18 17:55 ` Marcelo Tosatti
2021-03-19 9:35 ` Vitaly Kuznetsov
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