[vfio-users] Users of X99-boards, can you do me a small favor?

Hristo Iliev hristo at hiliev.eu
Sun Oct 2 22:52:05 UTC 2016

Am 01.10.2016 22:07, schrieb Martin Schrodt:
> Hi,
> after
> https://www.redhat.com/archives/vfio-users/2016-September/msg00114.html
> was not sufficiently answered, resulting in me spending two more days
> into finding a cure, I'm ready to give up. I'm about to switch to X99.
> To do it, I need to be sure the mainboard I'm gonna buy does not have
> the bug I am suffering on.
> Could you please do a
> cat /sys/devices/system/clocksource/clocksource0/available_clocksource
> after a suspend/resume cycle and confirm it shows
> tsc hpet acpi_pm
> on your board. If it does, would you please state here what kind of
> board you have?

No need to sleep/wake - my X99-based system starts with TSC disabled:

$ dmesg | grep TSC
[    0.000000] tsc: Fast TSC calibration using PIT
[    0.077986] TSC deadline timer enabled
[    0.203383] TSC synchronization [CPU#0 -> CPU#1]:
[    0.203384] Measured 974558547804462 cycles TSC warp between CPUs, 
turning off TSC clock.
[    0.203388] tsc: Marking TSC unstable due to check_tsc_sync_source 

Consequently, tsc is not among the clock sources listed in 
available_clocksource. KVM is not happy about that:

[16739.200656] kvm: SMP vm created on host with unstable TSC; guest TSC 
will not be reliable

But I haven't observed any instabilities of the Windows 10 guest, which 
happily runs with 4 virtual CPUs (2 virtual hyperthreaded CPUs) bound to 
two cores of my i7-5820K.

For the record, the motherboard is Gigabyte GA-X99-UD4 with BIOS version 


> Thank's a lot!
> Martin

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