Re: [PATCH 3/9] Implement GIF, clgi and stgi

[Avi Kivity <avi@qumranet.com>]

Alexander Graf wrote:
>
> Ah, so we don't sync hflags with the userspace on every transition but 
> only request it on save/restore?


Yes.  That's how all of the other state is synced.

>>>
>>> Do we really want to support storing the state when within the 
>>> Level2 VM? Can't we just #VMEXIT as soon as we switch to userspace 
>>> or so? That would probably simplify things a lot.
>>>
>>
>> Great idea.  What do we give as the exit reason?
>
> I thought of INTR here. That should be a nop in every VMM. Even if 
> not, worst case it would end in an hlt that still fires on the next 
> timer. 

Yes.  Luckily svm doesn't support capturing the vector number like vmx does.

There's only one case where this doesn't work, AFAICT: when the INTR 
intercept isn't enabled.  Once can think of a microkernel hypervisor 
that forwards all interrupts to a privileged guest (and when that guest 
is running, it can disable INTR intercepts).  I don't know of any 
hypervisor which does this (Xen doesn't and can't), so I don't think 
this is an objection to using INTR.

-- 
error compiling committee.c: too many arguments to function