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

[Hristo Iliev]

Am 04.10.2016 18:32, schrieb Brett Peckinpaugh:

> What are you settling that fixes the Nvidia experience complaint?
> 

In the domain description:

   <cpu mode='host-passthrough'>
     <topology sockets='1' cores='2' threads='2'/>
   </cpu>

And ignore_msrs=1 in the options to the kvm kernel module.

Apparently NVIDIA GFE is happy with i7-5820K having only two cores.

Cheers,
Hristo

>> On October 4, 2016 9:15:56 AM PDT, Hristo Iliev <hristo at hiliev.eu> 
>> wrote:
>> 
>> Hi Martin,
>> 
>> Am 04.10.2016 10:09, schrieb Martin Schrodt:
>> Hi Hristo,
>> 
>> 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
>> failed
>> 
>> 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
>> Ok, so an X99-board that behaves like this even on a fresh start.
>> Interesting.
>> 
>> 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.
>> This really makes me think there's something else involved in this
>> behaviour. Maybe the CPU configuration (I use "Skylake-Client") 
>> exposes
>> TSC to the guest, so if you put that on, it'll use it?
>> 
>> Can you check what kind of virtual CPU you use?
> 
> I use 'passthrough', otherwise the default 'Haswell-noTSX' that
> virt-manager picks results in NVIDIA GeForce Experience complaining
> about unrecognised CPU
> type, so the TSC gets pretty much exposed to the
> guest.
> 
> Just found this paste with a boot log from another system with the same
> motherboard, though with an older BIOS version and a Xeon E5-1620 v3
> CPU:
> 
> https://pastelink.net/fjm
> 
> It shows the same problem with unsynchronised TSCs. Could also be
> something specific to the LGA 2011v3 processors or to the EFI BIOS. 
> I'll
> take a look in the BIOS options when time permits.
> 
>> Cheers,
>> Martin
> 
> Cheers,
> Hristo