The existing guest debugging interface of kvm is limited in several ways:

 - depends on hardware breakpoints, thus suffers from running out of
   this scarce resource.
 - assumes that there are only 4 hardware breakpoints (even if some
   archs may once provide more)
 - doesn't support watchpoint or additional arch-specific debugging
   features

This patch series reworks the interface, providing usable software-based
breakpoint support, but also laying the ground for patches under
development that will add full hardware debugging features.

Content:
 Patch 1 - Replace KVM_DEBUG_GUEST with KVM_SET_GUEST_DEBUG interface,
           implement kernel side support
 Patch 2 - Tiny helper that allows pause and resume for a single vcpu
 Patch 3 - Userland changes that adopt KVM_SET_GUEST_DEBUG and switch to
           software breakpoints

Depends on:
 - "Fix monitor and gdbstub deadlocks v2" [1]
 - "Proper vm_stop on debug events" [2]

It's late here and the series is still fresh, but everything seems to
works nicely - even using gdb inside the guest while the host has active
breakpoints on the guest as well.

Looking forward to feedback and review.

Jan

[1] http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/17444
[2] http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/17775