lkml.org 
[lkml]   [2016]   [Oct]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/3] kvm: x86: do not use KVM_REQ_EVENT for APICv interrupt injection
From
Date
On 2016/9/28 19:50, Paolo Bonzini wrote:
>
>
> On 28/09/2016 13:40, Wu, Feng wrote:
>> IIUIC, the issue you describe above is that IPI for posted-interrupts may be
>> issued between
>>
>> vcpu->mode = IN_GUEST_MODE;
>>
>> and
>>
>> local_irq_disable();
>>
>> But if that really happens, we will call kvm_vcpu_kick() in
>> vmx_deliver_posted_interrupt(), hence the vcpu->mode will be changed
>> to EXITING_GUEST_MODE, then we will goto cancel_injection in
>> vcpu_enter_guest, so the posted-interrupt will be delivered to guest
>> in the next vmentry. Seems I cannot see the problem. Do I miss something?
>
> No, if that happens kvm_trigger_posted_interrupt returns true, hence
> kvm_vcpu_kick is not called. With the fix, the IPI is processed as soon
> as the guest enters non-root mode, and the interrupt is injected.
>
>
> The other issue occurs when the IPI is sent between
>
> kvm_x86_ops->hwapic_irr_update(vcpu,
> kvm_lapic_find_highest_irr(vcpu));
>
> and
>
> vcpu->mode = IN_GUEST_MODE;
>
> In this case, kvm_vcpu_kick is called but it (correctly) doesn't do
> anything because it sees vcpu->mode == OUTSIDE_GUEST_MODE. Then the
> guest is entered with PIR.ON, but the PI interrupt is not pending and
> hence the interrupt is never delivered to the guest. The fix for this
> is to move the RVI update after IN_GUEST_MODE. Then the source CPU uses
> the posted interrupt IPI instead of kvm_cpu_kick, and everything works.

Please ignore my previous reply. It seems you already aware the issue
and get the resolution to fix it.:-)


--
Yang
Alibaba Cloud Computing

\
 
 \ /
  Last update: 2016-10-14 09:38    [W:0.052 / U:5.556 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site