Re: High vm-exit latencies during kvm boot-up/shutdown

[Jan Kiszka <jan.kiszka-kv7WeFo6aLtBDgjK7y7TUQ@public.gmane.org>]

Avi Kivity wrote:
> Jan Kiszka wrote:
>> Got it! It's wbinvd from smm_init in rombios32.c! Anyone any comments on
>> this?
>>   
> 
> Ha!  A real life 300usec instruction!
> 
> Unfortunately, it cannot be trapped on Intel (it can be trapped on 
> AMD).  Looks like a minor hole in VT, as a guest can generate very high 
> latencies this way.

I unfortunately do not have an AMD box at hand to test (I obviously
order the wrong processor then...), but does this mean it is trapped by
kvm-amd already? Or would there be more work required on that side?

> 
> For our bios, we can remove it, but there's no way to ensure an 
> untrusted guest doesn't use it.

Yep. Any ideas if and at which stages (bootup, normal operation) Windows
is issues wbinvd noise?

Jan

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux

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