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From: | Hu Yaohui |
Subject: | Re: [Qemu-devel] Fwd: Guest VM debug (Int 3 panic) |
Date: | Thu, 26 Sep 2013 10:14:06 -0400 |
On 2013-09-25 20:08, Hu Yaohui wrote:"set arch" is unneeded. vmlinux already tells gdb that you are debugging
> 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
x86-64.
You can use hardware breakpoints as well but it is not required unless
> 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
the target code can be overwritten (e.g. due to a reset).
You didn't tell us which version of QEMU (or is it old qemu-kvm?) you
> "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.
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).
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.
Jan
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