Re: [PATCH 00/17] kvm-userspace: Fix and improve guest debugging and x86 debug registers

[Avi Kivity <avi@redhat.com>]

Jan Kiszka wrote:
> While still waiting on the required merge of the QEMU bits in this
> series (sigh...), I want to provide an update of my guest debugging and
> x86 debug register improvement patches. First comes the kvm-userspace
> part, kernel bits follow in a separate series.
>
> No new features since my last posting. But thanks to heavy internal use,
> I was able to identify and fix several tricky corner case (/wrt VMX).
> The changes are:
>  - rebased on top of the QEMU base series
>  - fixed single-stepping over STI and MOV SS/POP SS (VMX)
>  - proper compat wrapping for set_debugreg
>  - cleanup special_reload_dr7
>  - proper injection of soft exceptions like #BP (VMX)
>
> To summarize the contributions of this series (+ its related kernel
> bits):
>  - fully functional guest debugging via gdbstub,
>    including hardware breakpoints and watchpoints
>    (pick up current gdb cvs to have hbreak via remote gdb)
>  - (Almost) unlimited number of standard breakpoints
>  - SMP guest debugging support
>  - x86 debug registers support (makes guest's gdb and kgdb happy)
>
> The patches are in daily use for several moons here and have proven to
> be very helpful for tricky kernel debugging task. Specifically,
> reproducing and then tracking down certain races/deadlocks on SMP boxes
> is far more comfortable with KVM than on "real metal".
>   

I'm no expert on the qemu debugger, but apart for a few minor comments 
(sent as replies to the relevant patches) this looks good to me.

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