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

[Jan Kiszka <jan.kiszka@siemens.com>]

Avi Kivity wrote:
> 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.

Thanks a lot for reviewing, specifically also the QEMU part! Will look
into the details later, but they make sense on first glance.

Jan

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