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Groups > linux.debian.kernel > #63314
| From | Ewen McNeill <debbugs@ewen.mcneill.gen.nz> |
|---|---|
| Newsgroups | linux.debian.bugs.dist, linux.debian.kernel |
| Subject | Bug#918036: linux: uptime after reboot wrong (kvm-clock related?) |
| Date | 2019-02-10 23:50 +0100 |
| Message-ID | <xq65b-72Z-7@gated-at.bofh.it> (permalink) |
| References | <xbRfH-o8-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Cross-posted to 2 groups.
I'm also seeing this issue, also on a Debian Linux 4.19 kernel (on updated Debian unstable VM), also on KVM, straight after rebooting the VM. But without any suspending involved, I just reboot the VM, and as soon as I can log in after rebooting its showing 6+ days of uptime. The uptime jumps *very* early in the boot sequence, at the point that kvm-clock starts reporting, by many days in my case. Of note, the KVM host here is pretty old (Ubuntu 14.04 LTS, on 3.13.0-164-generic kernel, and qemu-kvm 2.0.0+dfsg-2ubuntu1.44). It's also naturally a fairly old CPU (Intel Xeon X3450). So I wonder if part of the trigger is newer (4.19) kernels relying on CPU/hypervisor features that older CPUs / older hypervisors do not provide/initialise. And maybe reading an uninitialised value as a result. From reading the upstream thread, this seems the closest to diagnosis: https://lore.kernel.org/lkml/20190126020410.GB3796@feynman.vault24.org/ around guest clock sources being chosen, and apparently the upstream maintainer has managed to reproduce the issue: https://lore.kernel.org/lkml/20190126161137.gme4vsrz3xmncbkx@soleen.tm1wkky2jk1uhgkn0ivaxijq1c.bx.internal.cloudapp.net/ by changing the clock source (to HPET), as of late Jan 2019. Ewen -=- cut here -=- ewen@debian-unstable:~$ uptime 11:21:06 up 6 days, 22:40, 1 user, load average: 0.88, 0.75, 0.52 ewen@debian-unstable:~$ last | head -5 ewen pts/0 172.20.254.10 Mon Feb 11 11:10 still logged in reboot system boot 4.19.0-2-amd64 Mon Feb 11 11:07 still running ewen ttyS0 Mon Feb 11 11:06 - down (00:00) ewen pts/0 172.20.254.10 Mon Feb 11 11:06 - down (00:00) reboot system boot 4.19.0-2-amd64 Mon Feb 11 11:05 - 11:06 (00:01) ewen@debian-unstable:~$ date Mon Feb 11 11:21:21 NZDT 2019 ewen@debian-unstable:~$ ewen@debian-unstable:~$ uname -r 4.19.0-2-amd64 ewen@debian-unstable:~$ dpkg -l | grep linux-image ii linux-image-4.19.0-1-amd64 4.19.13-1 amd64 Linux 4.19 for 64-bit PCs (signed) ii linux-image-4.19.0-2-amd64 4.19.16-1 amd64 Linux 4.19 for 64-bit PCs (signed) ii linux-image-amd64 4.19+102 amd64 Linux for 64-bit PCs (meta-package) ewen@debian-unstable:~$ ewen@debian-unstable:~$ sudo dmesg | grep -A 4 "Hypervisor" [ 0.000000] Hypervisor detected: KVM [ 0.000000] kvm-clock: Using msrs 4b564d01 and 4b564d00 [599207.077513] kvm-clock: cpu 0, msr 117d7001, primary cpu clock [599207.077513] clocksource: kvm-clock: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns [599207.077516] tsc: Detected 2659.982 MHz processor ewen@debian-unstable:~$ ewen@debian-unstable:~$ sudo dmesg | head -20 | grep -v BIOS-e820 [ 0.000000] Linux version 4.19.0-2-amd64 (debian-kernel@lists.debian.org) (gcc version 8.2.0 (Debian 8.2.0-14)) #1 SMP Debian 4.19.16-1 (2019-01-17) [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-4.19.0-2-amd64 root=UUID=260df8b9-6a61-4f0e-9625-340dcdaf4017 ro console=ttyS0,9600 [ 0.000000] x86/fpu: x87 FPU will use FXSAVE [ 0.000000] BIOS-provided physical RAM map: [ 0.000000] NX (Execute Disable) protection: active [ 0.000000] SMBIOS 2.4 present. [ 0.000000] DMI: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 [ 0.000000] Hypervisor detected: KVM [ 0.000000] kvm-clock: Using msrs 4b564d01 and 4b564d00 [599207.077513] kvm-clock: cpu 0, msr 117d7001, primary cpu clock [599207.077513] clocksource: kvm-clock: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns [599207.077516] tsc: Detected 2659.982 MHz processor [599207.078351] e820: update [mem 0x00000000-0x00000fff] usable ==> reserved ewen@debian-unstable:~$ -=- cut here -=- -=- cut here -=- ewen@naosdell:~$ head -5 /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 30 model name : Intel(R) Xeon(R) CPU X3450 @ 2.67GHz ewen@naosdell:~$ -=- cut here -=-
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Bug#918036: linux: uptime after reboot wrong (kvm-clock related?) Ewen McNeill <debbugs@ewen.mcneill.gen.nz> - 2019-02-10 23:50 +0100
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