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From:   Pavel Tatashin <pasha.tatashin@soleen.com>
Date:   Mon, 7 Jan 2019 13:17:16 -0500
Message-ID: <CA+CK2bDj1f=VpT+k-e8kSSaoLJ3W9-JPPq9udFdDwd6ijXi28g@mail.gmail.com>
Subject: Re: [PATCH v15 23/26] sched: early boot clock
To:     Dominique Martinet <asmadeus@codewreck.org>
Cc:     Salvatore Bonaccorso <carnil@debian.org>,
        Steven Sistare <steven.sistare@oracle.com>,
        Pavel Tatashin <pavel.tatashin@microsoft.com>,
        Daniel Jordan <daniel.m.jordan@oracle.com>,
        linux@armlinux.org.uk, schwidefsky@de.ibm.com,
        heiko.carstens@de.ibm.com, John Stultz <john.stultz@linaro.org>,
        sboyd@codeaurora.org, x86@kernel.org,
        LKML <linux-kernel@vger.kernel.org>, mingo@redhat.com,
        Thomas Gleixner <tglx@linutronix.de>, hpa@zytor.com,
        douly.fnst@cn.fujitsu.com, Peter Zijlstra <peterz@infradead.org>,
        prarit@redhat.com, feng.tang@intel.com,
        Petr Mladek <pmladek@suse.com>, gnomes@lxorguk.ukuu.org.uk,
        linux-s390@vger.kernel.org, boris.ostrovsky@oracle.com,
        jgross@suse.com, pbonzini@redhat.com,
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        qemu-devel@nongnu.org
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On Thu, Jan 3, 2019 at 6:43 PM Dominique Martinet
<asmadeus@codewreck.org> wrote:
>
> Pavel Tatashin wrote on Thu, Jan 03, 2019:
> > Could you please send the config file and qemu arguments that were
> > used to reproduce this problem.
>
> Running qemu by hand, nothing fancy e.g. this works:
>
> # qemu-system-x86_64 -m 1G -smp 4 -drive file=/root/kvm-wrapper/disks/f2.img,if=virtio -serial mon:stdio --enable-kvm -cpu Haswell -device virtio-rng-pci -nographic
>
> (used a specific cpu just in case but normally runnning with cpu host on
> a skylake machine; can probably go older)
>
>
> qemu is fedora 29 blend as is:
> $ qemu-system-x86_64 --version
> QEMU emulator version 3.0.0 (qemu-3.0.0-3.fc29)
> Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
>
>
> compressed .config attached to the mail, this can likely be trimmed down
> some as well but that takes more time for me..
> I didn't rebuild the kernel so not 100% sure (comes from
> /proc/config.gz) but it should work on a 4.20-rc2 kernel as written in
> the first few lines; 857baa87b64 I referred to in another mail was
> merged in 4.19-rc1 so anything past that is probably OK to reproduce...
>
>
> Re-checked today with these exact options (fresh VM start; then suspend
> laptop for a bit, then reboot VM):
> [    0.000000] Hypervisor detected: KVM
> [    0.000000] kvm-clock: Using msrs 4b564d01 and 4b564d00
> [ 2477.907447] kvm-clock: cpu 0, msr 153a4001, primary cpu clock
> [ 2477.907448] clocksource: kvm-clock: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns
> [ 2477.907450] tsc: Detected 2592.000 MHz processor

I could not reproduce the problem. Did you suspend to memory between
wake ups? Does this time jump happen every time, even if your laptop
sleeps for a minute?

I have tried with qemu 2.6 and 3.1 on Ubuntu, testing 4.20rc2.

Pasha