Re: [Qemu-devel] QEMU TB Unlinking due to interrupt.

[陳韋任]

On Tue, Dec 13, 2011 at 08:29:50PM -0500, Xin Tong wrote:
> QEMU performs a recursive unchaining on the current executing tb when
> a timer fires.  This timer is set by setitimer in the qemu-timer.c.
                        
  You mean dynticks_start_timer?

> This is what I mean by "interrupt pending". Of course, there are
> interrupts from emulated devices as well, but i do not know how that
> is set up, i.e. how tcg_handle_interrupt is called when the devices
> finishes some work. I hope you can enlighten me on that.

  I am not familiar with how QEMU deal with virtual devices. But AFAIK, virtual
devices will register IRQ to APIC (hw/apic.c), APIC will call cpu_interrupt
(cpu-all.h), which turns to call cpu_interrupt_handler. You can see 
cpu_interrupt_handler
is assigned as tcg_handle_interrupt in exec.c.  tcg_handle_interrupt raise env's
interrupt_request, and leave cpu_exec to check env's interrupt_request. 

Regards,
chenwj

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj