On Thu, Sep 29, 2011 at 7:55 AM, 陳韋任 <che...@iis.sinica.edu.tw> wrote: > Hi, all > > I am looking for when TB unchaining is needed. Currently, I > can only see there are three spots (take i386-softmmu as an > example): > > 1. cpu_interrupt: > > When virtual devices raise interrupts, eventually apic_local_deliver > (apic.c) will call cpu_interrupt. cpu_interrupt will set up > env->interrupt_request, then call cpu_unlink_tb to unlink env's > TBs. > > Here I have a question. I though cpu_interrupt is only used > in system mode to deliever virtual devices' interrupt. But it > seems process mode also has cpu_interrupt. > > I have ran some small programs in process mode under GDB, but > I never see cpu_interrupt is called. Do I have to run something > bigger to see when cpu_interrupt is called in process mode? Or > cpu_interrupt in process mode is only used in some rare cases?
I don't think it is possible. The only non-device cases for x86 are tb_invalidate_phys_page_range(), cpu_x86_set_a20() and do_inject_x86_mce(), none of which should be reachable from user emulator. Maybe these should be #ifdeffed out from user emulator builds. > 2. cpu_exit: > > QEMU will register a host SIGALRM handler, host_alarm_handler > (qemu-timer.c), when initialize the enviroment in system mode. > Then when host OS delivers SIGALRM to QEMU, host_alarm_handler > calls qemu_notify_event -> cpu_exit. cpu_exit raise env->exit_request > , then call cpu_unlink_tb to unlink env's TBs. > > There are other places where cpu_exit is called, like > > - cpu_signal: I think this is used when IOTHREAD is enabled. > > - DMA_init: I guess cpu_exit is called when DMA is done so > that control is gave back to QEMU from the code > cache. Yes, this is a questionable hack to improve performance. Maybe it's also not needed anymore since I/O thread was enabled. > - gdb_do_syscall: Don't know when it get called. > > - vm_stop -> cpu_stop_current: Don't know when it get called. grep -r is your friend. > 3. tb_phys_invalidate: > > QEMU will invalidate TBs related to a guest page which is > done by tb_invalidate_phys_page_range (exec.c), then > tb_invalidate_phys_page_range calls tb_phys_invalidate to > invalidate a TB and unlink links to the TB. > > > Please correct me if I am wrong or something miss. Thanks! > > > 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 > >
