Hi Jan, Thanks for your reply. On Thu, Sep 26, 2013 at 2:08 AM, Jan Kiszka <jan.kis...@web.de> wrote:
> On 2013-09-25 20:08, Hu Yaohui wrote: > > Hi All, > > I am trying to debug guest OS through qemu with kvm enabled. > > Following is what I have done: > > 1: fire the qemu-kvm > > <snip> > > sudo qemu-system-x86_64 -hda vdisk.img -m 4096 -smp 2 -vnc :2 -boot c -s > > </snip> > > > > 2: wait until login into guest OS (ubuntu 10.04) > > > > 3: fire gdb > > <snip> > > gdb vmlinux > > target remote :1234 > > b do_fork > > set arch i386:x86-64 > > "set arch" is unneeded. vmlinux already tells gdb that you are debugging > x86-64. > > > c > > </snip> > > > > 4: after I typed "ls" in guest OS. The guest OS paniced with some message > > related to "int 3 blah blah". Then crashed. > > > > Someone said we should use hardware breakpoint when kvm is enabled, or > > You can use hardware breakpoints as well but it is not required unless > the target code can be overwritten (e.g. due to a reset). > > > "monitor system_reset" after set the breakpoint, but it didn't work for > me. > > The hardware breakpoint could not been hit anyway. > > > > I have tried with "-no-kvm", it works normally with breakpoints. But I > want > > to debug the guest OS with kvm enabled. I don't know whether someone has > > met this similar situation. > > You didn't tell us which version of QEMU (or is it old qemu-kvm?) you > are using, what host kernel and which CPU type (AMD vs. Intel). Did you > try a recent version of all of them already? I'm currently not aware of > gdb problems with QEMU/KVM, I'm rather using it on an almost daily basis > (typically git head versions). > I am using a nested VM. My CPU type is intel. On L0, the QEMU-KVM version is 1.0, host kernel version: 2.6.32.10, kvm-kmod version: 3.2 On L1, the QEMU-KVM version is 1.2, kernel version: 3.2.2, kvm-kmod version: 3.2 On L2, guest kernel version: 2.6.32.10 I am trying to debug L2 guest kernel on L1 QEMU. It gives me "INT 3" related kernel oops. I also have tried to debug the L1 guest kernel through L0 QEMU which works fine. > > If you want to debug your issue: there is ftrace to record what KVM > events happen, and you can switch gdb into verbose mode as well, > comparing the communication between KVM on/off: set debug remote 1. > > Thanks for your suggestion! I will give that a try. > Jan > > >
