* Re: Tracking nested guest ioctl in L0 hypervisor
2012-07-31 3:50 Tracking nested guest ioctl in L0 hypervisor siddhesh phadke
@ 2012-08-01 10:52 ` Nadav Har'El
0 siblings, 0 replies; 2+ messages in thread
From: Nadav Har'El @ 2012-08-01 10:52 UTC (permalink / raw)
To: siddhesh phadke; +Cc: kvm
On Mon, Jul 30, 2012, siddhesh phadke wrote about "Tracking nested guest ioctl in L0 hypervisor":
> I am trying to understand KVM code for nested virtualization and my
> goal is to find whether an ioctl performed by L2 guest can be
> intercepted in L0.
>
> Hence just for experimental purpose I wrote an blank ioctl in L2
> guest. When that ioctl is received by L1 KVM hypervisor ,it uses
> kvm_hypercall0() mentioned in kvm_para.h to notify L0. Am I doing this
> correct or is there any other method to do the same or I am completely
> off the track?
>
> Can anyone please help me with this?
Do you really mean an *ioctl* in L2 - which is just a system call in
L2 (and never intercepted by L0 or L1), or a *hypercall*? From the
mention of kvm_hypercall0() it sounds like you mean a hypercall.
As you can see in vmx.c, nested_vmx_exit_handled(), when L0 receives
a VMCALL exit (i.e., a hypercall) from L2, we return 1 - meaning that
we exit to L1 so that it can handle this hypercall.
I believe that this is this is the more sensible behavior, but if you
want L0 to handle hypercalls, you can, in the EXIT_REASON_VMCALL case
in that function, return 0, which would cause L0 to handle this exit.
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Nadav Har'El | Wednesday, Aug 1 2012, 13 Av 5772
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