Re: [Qemu-devel] Re: [PATCH 0/7] KVM SMP support, early version

[Jan Kiszka]

Avi Kivity wrote:
> On 11/30/2009 07:30 PM, Jan Kiszka wrote:
>>>> No.  But what's wrong with on_vcpu?
>>>>        
>>> intrinsically racy. signal passing slow down things, etc.
>>>
>>> That said, as I've stated many times: I don't believe there's anything
>>> fundamentally wrong with on_vcpu. But we might get benefits from a re-design
>>> of things to avoid it whenever possible. (just like the vcpu_reset()
>>> I've just posted)
>>>
>>>      
>> If you don't want immediate execution of update_guest_debug, save the
>> state that shall be transferred, set some flag, and run the transfer
>> before guest entry inside the vcpu threads (after putting the registers
>> as older kernels may otherwise overwrite the flags register). Should
>> work, may even avoid redundant calls during a gdb session.
>>    
> 
> There's no guarantee the vcpu will ever exit to qemu, so you have to 
> signal the vcpu thread anyway.  When you do that, you might as well load 
> the new state.

Debugging is special here as it involves vmstop before you start playing
with the debug settings. But I may also oversee some corner case right now.

Jan

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