Re: Nested SVM and migration

Avi Kivity
2010-02-22T17:11:04Z

On 02/22/2010 07:07 PM, Zachary Amsden wrote:
> On 02/22/2010 07:02 AM, Avi Kivity wrote:
>> On 02/22/2010 07:00 PM, Zachary Amsden wrote:
>>>> The force vmexit would generate an INTR #vmexit even if the INTR
>>>> intercept was disabled and even if no INTR is pending. However
>>>> this was shot down since there was no equivalent vmx exit reason
>>>> that we can except the guest to reasonably handle.
>>>
>>>
>>> While true, my point is more precisely - how can this possibly work
>>> for guests which MUST never exit SVM? As in, the hypervisor is
>>> broken or deliberately disabled from taking exits, and in fact, may
>>> no longer even exist in memory?
>>
>> These guests will be broken. My assumption was that only malicious
>> guests will disable INTR intercepts (though I can imagine a
>> Luvalley-like system that disables INTR intercepts when running dom0).
>
> Not an SVM expert, but can't you pass through INTR in SVM and leave a
> fully functioning guest which technically runs under SVM but requires
> no hypervisor?

You could, but without trapping INTR, you can't reliably multiplex
guests or have a hypervisor-controlled network interface. That means
you're likely a blue pill thing.

> Is that what the Luvalley system does?

Luvalley is vmx only at the moment, but it certainly could let its dom0
handle interrupts (since the scheduler and all device drivers are in
dom0). Once it switches to a different guest, it needs to enable INTR.

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