Re: [PATCH 20/24] Correct handling of interrupt injection

["Nadav Har'El" <nyh@math.technion.ac.il>]

On Mon, Jun 14, 2010, Avi Kivity wrote about "Re: [PATCH 20/24] Correct handling of interrupt injection":
>..
> >However, properly doing what is described above requires invasive changes 
> >to
> >the flow of the existing code, which we elected not to do in this stage.
> >Instead we do something more simplistic and less efficient: we modify
>...
> 
> That's a little sad.

I agree. I'd like to change this code to do the proper thing (as I explained
in the patch's description), but as I said this will require some invasive
changes to existing KVM code outside vmx.c.
So seeing that this existing code also works, and despite hurting performance
a bit there are much more pressing performance issues (namely, the need
for nested EPT) - with your permission I'd like to postpone fixing this issue.

> >  static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu)
> >  {
> >+	if (to_vmx(vcpu)->nested.nested_mode&&  nested_exit_on_intr(vcpu)) {
> >+		if (to_vmx(vcpu)->nested.nested_run_pending)
> >+			return 0;
> >+		nested_vmx_vmexit(vcpu, true);
> >+		/* fall through to normal code, but now in L1, not L2 */
> >+	}
> >+
> >   
> 
> What exit is reported here?

When nested_vmx_vmexit is called with the second parameter true, as above,
it modifies the (vmcs12) exit reason to	be EXIT_REASON_EXTERNAL_INTERRUPT.
A hack, but it does the right thing in this case because L1 doesn't even get
a chance to care about this exit reason before it exits again (as I tried to
explain in the patch's description).

-- 
Nadav Har'El                        |     Thursday, Sep 16 2010, 8 Tishri 5771
nyh@math.technion.ac.il             |-----------------------------------------
Phone +972-523-790466, ICQ 13349191 |Debugging: the art of removing bugs.
http://nadav.harel.org.il           |Programming: the art of inserting them.