Re: Some questions from a freshman to this community

[Zhengwang Ruan <ruan.zhengwang@gmail.com>]

Hi guys,

Could you guys kindly help me answer these questions below? This is very 
helpful for me to learn kvm. Thanks! :-)

Regards,

Zhengwang


-------- Original Message --------
From: Zhengwang Ruan
Sent: 2012年06月26日 星期二 10时16分49秒
To: kvm
Subject: Some questions from a freshman to this community
> Hi all,
>
> I am freshman to this community, I have some questions roughly about 
> how does KVM work, please help me answer these questions, thank you!
>
> 1, What is the relation between kvm-mod and kvm-qemu?
>
> Is kvm-qemu mainly used to emulate the first initial 16-bit code of a 
> guest, then this qemu context will be replaced by the real guest, such 
> as linux, windows? But I also see some emulation code in kvm-mod, what 
> are these code used for?
>
> 2, How to handle irqs in kvm-mod?
>
> I found vmx_inject_irq is used to inject an interrupt to a guest by 
> writing vmcs for a guest, initialized by this call trace: vmx_init -> 
> kvm_init -> kvm_arch_init (kvm_x86_ops is assigned in this call), then 
> kvm_x86_ops will be used everywhere to set_irq for guests. Am I right?
>
> But I seems to me that vmx_inject_irq is only called by 
> .unlocked_ioctl in kvm_vcpu_fops file_operation struct, where could we 
> use this file operation? If a device wants to issue an interrupt to a 
> guest, how does this happen in device driver?
>
> 3, APIC.
>
> I see that each vcpu has a local apic (vcpu.arch->apic), and some 
> functions use this area ranged by this apic pointer to do setting and 
> reading. Is this used to emulate apic for each vcpu? If so, when and 
> where this will be used by guests?
>
> 4, The relation between kvm_vcpu_arch and vmcs.
>
> There are some regular registers in kvm_vcpu_arch, and the values for 
> these registers also be used to read and write. I am confused about 
> this, if we want to read/write a register for a guest, we don't 
> directly use those values in vmcs??
>
>
> Regards,
>
> Zhengwang
>