Re: VMX: Host NMI triggering on NMI vmexit

[Jan Kiszka <jan.kiszka@siemens.com>]

Yang, Sheng wrote:
> On Monday 22 September 2008 19:00:38 Avi Kivity wrote:
>> Jan Kiszka wrote:
>>>> Maybe the answer is to generate the local nmi via an IPI-to-self command
>>>> to the local apic.
>>> Going this way leaves me with a few questions: Will it be OK for the
>>> related mainainers to export the required service?
>> If we can make a case for it (I think we can), then I don't see why not.
>>
>> Sheng, can you confirm that 'int 2' is problematic, and that
>> nmi-via-lapic is the best workaround?
> 
> Just back from vacation... :)
> 
> Jan said is true, "int 2" itself won't block subsequent NMIs. But I think it's 
> too obviously as a hardware issue when using with NMI exiting=1 in vmx 
> nonroot mode, so I have checked it with my colleague, finally found these in 
> SDM 3B 23-2:
> 
> The following bullets detail when architectural state is and is not updated in 
> response to VM exits:
> •   If an event causes a VM exit *directly*, it does not update architectural 
> state as it would have if it had it not caused the VM exit:
> [...]
> — *An NMI causes subsequent NMIs to be blocked*, but only after the VM exit
>   completes.
> 
> So we needn't worry about that, and this shouldn't cause any trouble AFAIK...

Fine, problems--. :)

> 
> Jan, seems we need to do more investigating on the issues you met...

Sorry, which one do you mean now?

Jan

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