On 2013-09-26 16:14, Hu Yaohui wrote: > 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.
Oh, "minor" detail ;) - why nested? But this used to work for me with a patched 3.9+ kernel some while ago. > 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 Try at least the latest kvm-kmod version, but there are even more fixes in kvm.git. Not sure if any of them has direct impact on your scenario, but it's generally better to use a recent kernel with this still experimental feature (VMX nesting). As this is likely a KVM issue, I'm also CC'ing the corresponding list Jan > 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 >> >> >> >
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