> On Jan 24, 2020, at 3:38 PM, Sean Christopherson <sean.j.christopherson@xxxxxxxxx> wrote:
>
> On Fri, Jan 24, 2020 at 03:13:44PM -0800, Nadav Amit wrote:
>>> On Dec 2, 2019, at 12:43 PM, Aaron Lewis <aaronlewis@xxxxxxxxxx> wrote:
>>>
>>> Verify that the difference between a guest RDTSC instruction and the
>>> IA32_TIME_STAMP_COUNTER MSR value stored in the VMCS12's VM-exit
>>> MSR-store list is less than 750 cycles, 99.9% of the time.
>>>
>>> 662f1d1d1931 ("KVM: nVMX: Add support for capturing highest observable L2 TSC”)
>>>
>>> Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
>>> Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
>>
>> Running this test on bare-metal I get:
>>
>> Test suite: rdtsc_vmexit_diff_test
>> FAIL: RDTSC to VM-exit delta too high in 117 of 100000 iterations
>>
>> Any idea why? Should I just play with the 750 cycles magic number?
>
> Argh, this reminds me that I have a patch for this test to improve the
> error message to makes things easier to debug. Give me a few minutes to
> get it sent out, might help a bit.
Thanks for the quick response. With this patch I get on my bare-metal Skylake:
FAIL: RDTSC to VM-exit delta too high in 100 of 49757 iterations, last = 1152
FAIL: Guest didn't run to completion.
I’ll try to raise the delta and see what happens.
Sorry for my laziness - it is just that like ~30% of the tests that are
added fail on bare-metal :(
