Re: FW: [kvm-commits] KVM: Move interrupt injection out of interruptdisabled section

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

Dong, Eddie wrote:
> Wrong mailing list.
> Resend :-(
>
>   

(and here's a copy of my reply if someone is interested)

> Dong, Eddie wrote:
>   
>> Avi:
>> 	This patch may be questionable at least for current VMX.
>> 	If VM_ENTRY_INTR_INFO_FIELD is already set valid by
>> previous irq injection, next injection will be refused with IRQ window
>> enabled. This is because current implementation will inject exception
>> earlier than irq injection and vmx_intr_assist doesn;t know if
>> previous injected event is external irq (and thus overwrite) or
>> exception. Guest will see lower priority irq get injected rather than
>> higher 
>> priority IRQ which
>> arrives later.
>>
>>     

Well, the same thing happens with the code before this commit, no?  If a
high priority interrupt arrives after injection, it will have to wait. 
The difference is that before this commit, it woke up with the IPI and
now it notices with KVM_REQ_INTR.

The window grew larger, but not by much typically.



>> 	BTW, I didn't see obvious benfit from this patch since
>> inject_pending_irq still happens later after IRQ disable. maybe I
>> miss something. 
>>
>>     


That was accidental; I corrected it.



-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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