Re: [Xen-devel] Future x86 emulator direction

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

Hello, and first of all thanks for the discussion!

> Think of it a bit more like introducing a new action emulator (name
> definitely subject to improvement), which implements things such as
> wrmsr, cpuid, pagewalk, task_switch, etc.
> 
> The vmexit helpers, given decode assistance from hardware, can directly
> call action->task_switch().  If insufficient information is available
> (e.g. LMSW on AMD), the helpers invoke the instruction emulator to work
> out what to do, and the instruction emulator would invoke the action
> emulator as part of its execute phase.
> 
> Wherever possible, the action emulator should be guest-neutral, and
> ideally the single point of implementation of non-architectural actions
> such as "the vm_event subsystem is interested in this."
> 
>> And to be honest, on the road towards
>> completion of the emulator I think the SVM/VMX insns are pretty
>> close to the end of the priority list.
> 
> I'd expect them to show up frequently during introspection, although
> maybe I am wrong.  Razvan: Any thoughts?

I definitely think this is a good idea as far as introspection goes -
having a single contact surface with the underlying logic would be a
significant improvement.

As for SVM/VMX instructions, we're interested in anything that is able
to trigger an EPT fault (and hence a mem_access event) - we've had our
share of adventures with VMX-specific instructions, so they're not low
priority for us.


Thanks,
Razvan

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