RE: [PATCH] KVM: nVMX: Fix IRQs inject to L2 which belong to L1 since race

[Hu, Robert]

> -----Original Message-----
> From: Jan Kiszka [mailto:jan.kiszka@xxxxxxxxxxx]
> Sent: Wednesday, July 2, 2014 5:03 PM
> To: Hu, Robert; Wanpeng Li; Paolo Bonzini; Gleb Natapov
> Cc: kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH] KVM: nVMX: Fix IRQs inject to L2 which belong to L1 since
> race
> 
> On 2014-07-02 09:20, Hu, Robert wrote:
> >> -----Original Message-----
> >> From: Wanpeng Li [mailto:wanpeng.li@xxxxxxxxxxxxxxx]
> >> Sent: Wednesday, July 2, 2014 2:54 PM
> >> To: Paolo Bonzini; Jan Kiszka; Gleb Natapov
> >> Cc: Hu, Robert; kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Wanpeng
> Li
> >> Subject: [PATCH] KVM: nVMX: Fix IRQs inject to L2 which belong to L1 since
> race
> >>
> >> This patch fix bug https://bugzilla.kernel.org/show_bug.cgi?id=72381
> >>
> >> If we didn't inject a still-pending event to L1 since nested_run_pending,
> >> KVM_REQ_EVENT should be requested after the vmexit in order to inject the
> >> event to L1. However, current log blindly request a KVM_REQ_EVENT even if
> >> there is no still-pending event to L1 which blocked by nested_run_pending.
> >> There is a race which lead to an interrupt will be injected to L2 which
> >> belong to L1 if L0 send an interrupt to L1 during this window.
> >>
> >>                VCPU0                               another thread
> >>
> >> L1 intr not blocked on L2 first entry
> >> vmx_vcpu_run req event
> >> kvm check request req event
> >> check_nested_events don't have any intr
> >> not nested exit
> >>                                             intr occur (8254, lapic timer
> >> etc)
> >> inject_pending_event now have intr
> >> inject interrupt
> >>
> >> This patch fix this race by introduced a l1_events_blocked field in nested_vmx
> >> which indicates there is still-pending event which blocked by
> >> nested_run_pending,
> >> and smart request a KVM_REQ_EVENT if there is a still-pending event which
> >> blocked
> >> by nested_run_pending.
> >>
> >> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
> > Tested-by: Robert Hu<robert.hu@xxxxxxxxx>
> 
> Do you happen to have a kvm-unit-test for this race? Or how did you
> test? Just curious, and if there is a test, it would be good to
> integrate it.
I just apply the patch and test the reported scenario.
> 
> Jan
> 
> --
> Siemens AG, Corporate Technology, CT RTC ITP SES-DE
> Corporate Competence Center Embedded Linux
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