Re: kernel device reset support

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Dong, Eddie wrote:
> Avi Kivity wrote:
>   
>>> If BSP mp_state becomes VCPU_MP_STATE_UNINITIALIZED, current code
>>> can't wakeup it. We need additional code that I am not aware of now.
>>>
>>> Current VCPU must be BSP, otherwise the code executing in Qemu will
>>> have problem too. 
>>>
>>>       
>> But, for an ungraceful reset, nothing prevents an AP from
>> issuing a reset?
>>     
>
> Mmm, Yes, but I think current architecture can't handle this.
> The thread where AP issues "RESET" will continue run, which
> means it becomes BSP now and wake up other APs later on.
> Or We can block that AP first and then inform BSP to do 
> RESET job. Here we need to block the AP in kernel 
> so that we can wake up.
>   

It should call vcpu_halt() immediately after reset.

> It can be a future task which is not that high priority IMO. 
> I will focus on SMP boot 1st. Your opnion?
>   

Agree.  But let's make it close to the complete solution.

>>>
>>>       
>> What I mean is to use mp_state within the vcpu code (while holding the
>> vcpu mutex) and to use vcpu->requests as a means to tell the vcpu it
>> needs to change state. 
>>
>>     
>
> Then we need to add code to enter waitqueque here. I think force_to_quit
> is much simple and efficient since we don't need to test (atomic test) 
> at each VM Exit even light weight VM Exit.
>   

The test for vcpu->requests already exists (and is needed for tlb 
flushes) so there is no additional performance hit.

> But certainly it can. If you want to save the per VCPU force_to_quit, we
> can share it with vcpu_request, but test in external IRQ is better IMO
> since we take a kick now.
>   

The vcpu may have exited due to some other reason, and the interrupt 
taken in host context?


-- 
error compiling committee.c: too many arguments to function


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