Re: Kernel debugging with KVM?

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Jun Koi wrote:
> Hi,
>
> I am investigating the possibility of debugging guest kernel with KVM.
> Anybody may shed some lights into how KVM handles breakpoints?
>
> Suppose that we put a breakpoint (0xCC opcode in x86) into guest
> kernel. When the kernel hits the breakpoint, which one will handle the
> event?
>
> Looks like qemu will handle the breakpoint first, then next the guest
> kernel itself have a chance to process it. Is that correct?
>
> And is there any chance for the host (VMM) to get notified about the event?
>
>   

kvm supports using hardware breakpoints to debug a guest.  See the 
KVM_GUEST_DEBUG ioctl.

The modified qemu shipped with kvm allows gdb to connect and debug a kvm 
guest.  It's been a long while since I tested this, so it may or may not 
work.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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