Handle multiple interrupts injection in one vmexit

Handle multiple interrupts injection in one vmexit

[Arthur Chunqi Li]

Hi there,

External interrupts are injected in function vcpu_enter_guest, with
checking KVM_REQ_EVENT. If there are more than one interrupts in one
vmexit (e.g. nmi and external events occur concurrently in one
vmexit), KVM will handle only one interrupt of the highest priority
(e.g. NMI), right? So only NMI is injected in this vmexit, thus when
will the other external events injected? I don't see any extra setting
of KVM_REQ_EVENT to handle the lower priority interrupts injection in
KVM.

Thanks,
Arthur

-- 
Arthur Chunqi Li
Department of Computer Science
School of EECS
Peking University
Beijing, China

Re: Handle multiple interrupts injection in one vmexit

[Jan Kiszka]

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On 2014-05-26 15:51, Arthur Chunqi Li wrote:
> Hi there,
> 
> External interrupts are injected in function vcpu_enter_guest, with
> checking KVM_REQ_EVENT. If there are more than one interrupts in one
> vmexit (e.g. nmi and external events occur concurrently in one
> vmexit), KVM will handle only one interrupt of the highest priority
> (e.g. NMI), right? So only NMI is injected in this vmexit, thus when
> will the other external events injected? I don't see any extra setting
> of KVM_REQ_EVENT to handle the lower priority interrupts injection in
> KVM.

[you should mention that you are talking about x86 here]

If both events are pending, inject_pending_event will try to inject the
NMI. vcpu_enter_guest will then notice that there are still pending
interrupts and request the interrupt window vmexit. If the NMI should be
blocked, an NMI window exit is requested. But on NMI injection, another
KVM_REQ_EVENT is send (see e.g. handle_nmi_window in vmx.c).

Jan



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Re: Handle multiple interrupts injection in one vmexit

[Arthur Chunqi Li]

Thanks Jan.

On Mon, May 26, 2014 at 6:44 PM, Jan Kiszka <jan.kiszka@web.de> wrote:
> On 2014-05-26 15:51, Arthur Chunqi Li wrote:
>> Hi there,
>>
>> External interrupts are injected in function vcpu_enter_guest, with
>> checking KVM_REQ_EVENT. If there are more than one interrupts in one
>> vmexit (e.g. nmi and external events occur concurrently in one
>> vmexit), KVM will handle only one interrupt of the highest priority
>> (e.g. NMI), right? So only NMI is injected in this vmexit, thus when
>> will the other external events injected? I don't see any extra setting
>> of KVM_REQ_EVENT to handle the lower priority interrupts injection in
>> KVM.
>
> [you should mention that you are talking about x86 here]
>
> If both events are pending, inject_pending_event will try to inject the
> NMI. vcpu_enter_guest will then notice that there are still pending
> interrupts and request the interrupt window vmexit. If the NMI should be
> blocked, an NMI window exit is requested. But on NMI injection, another
> KVM_REQ_EVENT is send (see e.g. handle_nmi_window in vmx.c).
>
Yes, I see the Bit 2 (Interrupt-window exiting) and Bit 22 (NMI-window
exiting) on Primary Processor-Based VM-Execution Controls is used to
handle simultaneous (or contiguous) interrupt/NMI injection. See Intel
SDM Chapter 24.6.2 if any other guys need this information.

Arthur
> Jan
>
>



-- 
Arthur Chunqi Li
Department of Computer Science
School of EECS
Peking University
Beijing, China