Re: [PATCH v3 34/43] hw/intc: Add LoongArch extioi interrupt controller(EIOINTC)

[maobibo]

在 2022/5/11 22:14, Richard Henderson 写道:
> On 5/11/22 02:54, yangxiaojuan wrote:
>>
>> On 2022/5/10 上午1:56, Richard Henderson wrote:
>>>
>>>>>> +    case EXTIOI_IPMAP_START ... EXTIOI_IPMAP_END - 1:
>>>>>> +        index = (offset - EXTIOI_IPMAP_START) >> 2;
>>>>>> +        s->ipmap[index] = val;
>>>>>> +        break;
>>>>>
>>>>> Do you need to recompute the entire interrupt map when ipmap changes?
>>>>>
>>>> Sorry, could you explain it in more detail? i can not understand the 
>>>> meanning of 'the entire interrupt map'?
>>>
>>> I mean, ipmap[*] and coremap[*] controls how isr[*] maps to the various 
>>> cpus, as coreisr[*].  If either ipmap or coremap changes, do you need to 
>>> re-compute coreisr[*] from the input isr[*]? 
>>
>> I think the interrupt has been handled by the core before set coremap or 
>> ipmap, and coreisr[*] also has been set and cleard by original core.
>> So,  the new mapped core need not  to update the coreisr[*].
> 
> 
> Why do you believe that the core to which the interrupt is directed has 
> interrupts enabled?  Why do you believe the core to which the interrupt is 
> directed is the one that is changing the interrupt mapping?
By my understanding, irq bit of coreisr will be set even if the interrupt is 
disabled on the core, interrupt has been posted to core already, only that it 
is not serviced by the core. After irq affinity is changed, new interrupt may 
arrived to new core, one interrupt will be serviced by old core and new core at 
the same time. However it is the problem of guest kernel, guest kernel system 
should disable the irq and wait until irq finishes to be serviced on the old 
core when irq affinity is changing.

> 
> I think your assumption is not correct.
> 
> 
> r~