Re: [PATCH v2 04/15] kvm: x86: Add per-VM APICv state debugfs

[Suthikulpanit, Suravee]

Alex,

On 8/19/2019 4:57 AM, Alexander Graf wrote:
> 
> 
> On 15.08.19 18:25, Suthikulpanit, Suravee wrote:
>> Currently, there is no way to tell whether APICv is active
>> on a particular VM. This often cause confusion since APICv
>> can be deactivated at runtime.
>>
>> Introduce a debugfs entry to report APICv state of a VM.
>> This creates a read-only file:
>>
>> ÂÂÂ /sys/kernel/debug/kvm/70860-14/apicv-state
>>
>> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> 
> Shouldn't this first and foremost be a VM ioctl so that user space can inquire its own state?
> 
> 
> Alex

I introduce this mainly for debugging similar to how KVM is currently provides
some per-VCPU information:

     /sys/kernel/debug/kvm/15957-14/vcpu0/
         lapic_timer_advance_ns
         tsc-offset
         tsc-scaling-ratio
         tsc-scaling-ratio-frac-bits

I'm not sure if this needs to be VM ioctl at this point. If this information is
useful for user-space tool to inquire via ioctl, we can also provide it.

Thanks,
Suravee