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[Qemu-devel] [Bug 1086782] Re: HPET time drift windows 7 64bits guest

From: Carlos-velasco
Subject: [Qemu-devel] [Bug 1086782] Re: HPET time drift windows 7 64bits guest
Date: Mon, 06 Nov 2017 09:07:04 -0000

Testing now with qemu 2.10.1
Will need 1 day to see drift or not

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  HPET time drift windows 7 64bits guest

Status in QEMU:

Bug description:
  Using latest qemu-kvm (1.2.0), time drift (clock slow in guest) in Windows 7 
64 bits guest when HPET is enabled (default).
  Disabling HPET (-no-hpet) solves the time drift.

  UsePlatformClock enable/disable doesn't make a difference in the guest.
  bcdedit /set useplatformclock true

  Using driftfix slew doesn't make a difference too.

  # qemu-system-x86_64 --version
  QEMU emulator version 1.2.0 (qemu-kvm-1.2.0), Copyright (c) 2003-2008 Fabrice 

  Kernel is 3.6.8:
  # uname -a
  Linux pulsar 3.6.8 #1 SMP Sat Dec 1 16:26:10 CET 2012 x86_64 x86_64 x86_64 

  TSC is stable in the host:
  # cat /sys/devices/system/clocksource/clocksource0/current_clocksource

  [    0.000000] hpet clockevent registered
  [    0.000000] tsc: Fast TSC calibration using PIT
  [    0.000000] tsc: Detected 2660.096 MHz processor
  [    0.001002] Calibrating delay loop (skipped), value calculated using timer 
frequency.. 5320.19 BogoMIPS (lpj=2660096)
  [    0.001138] pid_max: default: 32768 minimum: 301
  [    1.492019] tsc: Refined TSC clocksource calibration: 2659.973 MHz
  [    1.492093] Switching to clocksource tsc

  CPUinfo, constant_tsc:
  vendor_id       : GenuineIntel
  cpu family      : 6
  model           : 23
  model name      : Intel(R) Core(TM)2 Quad CPU    Q8400  @ 2.66GHz
  stepping        : 10
  microcode       : 0xa0b
  cpu MHz         : 2667.000
  cache size      : 2048 KB
  flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca 
cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm 
constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor 
ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm dtherm tpr_shadow 
vnmi flexpriority
  bogomips        : 5320.19

  # grep -i hpet .config
  # CONFIG_HPET_MMAP is not set

  Qemu command line:
  /usr/bin/qemu-system-x86_64 -drive 
file=/dev/vol0/KVMORION01,cache=none,aio=native,if=virtio \
    -drive file=/dev/vol0/KVMORION02,cache=none,aio=native,if=virtio \
    -cpu host \
    -m 2048 \
    -smp 4,maxcpus=4,cores=4,threads=1,sockets=1 \
    -rtc base=localtime,driftfix=slew \
    -vnc,password -k es \
    -monitor telnet:localhost:37200,server,nowait \
    -device virtio-net-pci,netdev=kvmorion,id=virtio-nic0,mac=02:85:64:02:c2:aa 
    -device virtio-balloon-pci,id=balloon0 \
    -boot menu=on \
    -pidfile /var/run/kvmorion.pid \

  Using 1 CPU doesn't make a difference.
  Only workaround is disabling hpet (-no-hpet)

  Sample time drift in guest:
  >ntpdate -q
   5 Dec 13:36:06 ntpdate[3464]: Raised to realtime priority class
  server, stratum 2, offset 3.694184, delay 0.02551
   5 Dec 13:36:12 ntpdate[3464]: step time server offset 
3.694184 s

  >ntpdate -q
   5 Dec 13:52:02 ntpdate[1964]: Raised to realtime priority class
  server, stratum 2, offset 4.719968, delay 0.02554
   5 Dec 13:52:08 ntpdate[1964]: step time server offset 
4.719968 s

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