Re: [PATCH] [RFC] Fix for kvm qemu to return control to gdb stub on breakpoints

[Jan Kiszka <jan.kiszka@web.de>]

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Anthony Liguori wrote:
> Jan Kiszka wrote:
>> Jerone Young wrote:
>>  
>>> 1 file changed, 2 insertions(+)
>>> qemu/qemu-kvm.c |    2 ++
>>>
>>>
>>> Currently breakpoints do not fully work for x86 or any other arch
>>> with kvm enable qemu. Control is not being returned by to the gdb
>>> stub. This patch add back this ability to return control to the gdb
>>> stub when a debug interrupt is hit.
>>>
>>> This is in the io thread so it's best to get comments on this. Is it
>>> in the best place? Should more be done here?
>>>
>>> Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
>>>
>>> diff --git a/qemu/qemu-kvm.c b/qemu/qemu-kvm.c
>>> --- a/qemu/qemu-kvm.c
>>> +++ b/qemu/qemu-kvm.c
>>> @@ -352,6 +352,8 @@ static int kvm_main_loop_cpu(CPUState *e
>>>          update_regs_for_init(env);
>>>      if (!(env->hflags & HF_HALTED_MASK) && !info->init)
>>>          kvm_cpu_exec(env);
>>> +    if (env->exception_index == EXCP_DEBUG)
>>> +        vm_stop(EXCP_DEBUG);
>>>     
>>
>> This isn't enough, please see
>>
>>     http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/17660
>>
>> and the rest of that series - just RFC, but already usable.
>>   
> 
> While I haven't looked through your whole series, the io-thread caused a
> regression with gdb and while I don't think that this patch is enough of
> a fix, it's certainly the right idea for fixing that regression.
> 
> Soft breakpoints is a nice thing to do, but I think orthogonal to what
> this patch is addressing.

For sure this or a similar approach is required, and I'm fine if we fix
this beforehand. I just pointed to my series to avoid duplicate and
lengthy debugging of known and (hopefully) fixed issues. I already went
through this. :)

Jan


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