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

[Jayme Howard]

I can confirm that GFE doesn't care if the CPU doesn't match what the
physical CPU offers in terms of cores.  My i5-4670k is chugging along just
fine with 3 cores, as far as Windows knows.

On Tue, Oct 4, 2016 at 3:42 PM, Hristo Iliev <hristo at hiliev.eu> wrote:

> 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
>>
>
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