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Message-ID: <d18bb252013df73abc0de662008f399cf77e78cf.camel@infradead.org>
Subject: Re: [PATCH 1/1] KVM: selftests: add kvmclock drift test
From: David Woodhouse <dwmw2@infradead.org>
To: Dongli Zhang <dongli.zhang@oracle.com>, kvm@vger.kernel.org, 
	linux-kselftest@vger.kernel.org
Cc: pbonzini@redhat.com, shuah@kernel.org, seanjc@google.com, 
	linux-kernel@vger.kernel.org, joe.jin@oracle.com
Date: Thu, 04 Apr 2024 15:34:08 +0100
In-Reply-To: <20240106083346.29180-1-dongli.zhang@oracle.com>
References: <20240106083346.29180-1-dongli.zhang@oracle.com>
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On Sat, 2024-01-06 at 00:33 -0800, Dongli Zhang wrote:
> There is kvmclock drift issue during the vCPU hotplug. It has been fixed =
by
> the commit c52ffadc65e2 ("KVM: x86: Don't unnecessarily force masterclock
> update on vCPU hotplug").
>=20
> This is to add the test to verify if the master clock is updated when we
> write 0 to MSR_IA32_TSC from the host side.
>=20
> Here is the usage example on the KVM with the bugfix reverted.
>=20
> $ ./kvm_clock_drift -v -p 5
> kvmclock based on old pvclock_vcpu_time_info: 5012221999
> =C2=A0 version:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 2
> =C2=A0 tsc_timestamp:=C2=A0=C2=A0=C2=A0=C2=A0 3277968
> =C2=A0 system_time:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 11849519
> =C2=A0 tsc_to_system_mul: 2152530255
> =C2=A0 tsc_shift:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0
> =C2=A0 flags:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0 1
>=20
> kvmclock based on new pvclock_vcpu_time_info: 5012222411
> =C2=A0 version:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 4
> =C2=A0 tsc_timestamp:=C2=A0=C2=A0=C2=A0=C2=A0 9980576184
> =C2=A0 system_time:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 5012222411
> =C2=A0 tsc_to_system_mul: 2152530255
> =C2=A0 tsc_shift:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0
> =C2=A0 flags:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0 1
>=20
> =3D=3D=3D=3D Test Assertion Failure =3D=3D=3D=3D
> =C2=A0 x86_64/kvm_clock_drift.c:216: clock_old =3D=3D clock_new
> =C2=A0 pid=3D14257 tid=3D14257 errno=3D4 -  Interrupted system call
> =C2=A0=C2=A0=C2=A0=C2=A0 1=C2=A0=C2=A00x000000000040277b: main at kvm_clo=
ck_drift.c:216
> =C2=A0=C2=A0=C2=A0=C2=A0 2=C2=A0=C2=A00x00007f7766fa7e44: ?? ??:0
> =C2=A0=C2=A0=C2=A0=C2=A0 3=C2=A0=C2=A00x000000000040286d: _start at ??:?
> =C2=A0 kvmclock drift detected, old=3D5012221999, new=3D5012222411
>=20
> Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>

We should extend this to cover live update =E2=80=94 it should create a
*second* KVM, migrate the guest including its clock information to
that, and validate that the kvmclock information still doesn't change.

Ideally during a leap second.


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