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From: Stefan Hajnoczi <stefanha@gmail.com>
Date: Sat, 30 Jul 2016 09:35:58 +0100
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Subject: Re: [Qemu-devel] From virtio_kick until VM-exit?
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To: "Charls D. Chap" <chapcharls@gmail.com>
Cc: qemu-devel <qemu-devel@nongnu.org>

On Fri, Jul 29, 2016 at 9:00 PM, Charls D. Chap <chapcharls@gmail.com> wrote:

Please use Reply-All when responding to a mailing list thread.  This
keeps the mailing list (qemu-devel@nongnu.org) in the CC list so your
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stays public on the mailing list and others can participate.

> I've read again and again the code. Please let me ask you one last question.
>
> the question is, where is the VMEXIT and VMENTRY code.
>
>
> If i have this, i can answer the following that bother me:
> 1)
> What is a VMEXIT, what mechanism? is it an interrupt? Same for VMENTRY
> Where does the VMENTRY return? In an interrupt handler?
>
> 2)
> Which are the parameters of vmetry and vmexit
> does each vcpu has a specific VPID or does it change in every RESUME
>
> 3)
> What is a hypercall? A pair of VMEXIT-VMENTRY? or is it oneway (does it ever
> return?) Or there are many types of hypercalls
>
> 4)
> When we do vmexit, Is it another context? I am mean, does the stack changes?
> What is the guest stack? Each vcpu has one stack?

Please look at the Intel Software Developer's Manuals and read about
VMX instructions:

https://www-ssl.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html

Once you have an overview you'll understand the semantics and be able
to grep for the relevant code in the kvm kernel module.

Stefan