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SubjectRe: [PATCH 3/3] KVM: nVMX: Clear IDT vectoring on nested VM-Exit for double/triple fault
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On 4/7/2022 8:23 AM, Sean Christopherson wrote:
> Clear the IDT vectoring field in vmcs12 on next VM-Exit due to a double
> or triple fault. Per the SDM, a VM-Exit isn't considered to occur during
> event delivery if the exit is due to an intercepted double fault or a
> triple fault. Opportunistically move the default clearing (no event
> "pending") into the helper so that it's more obvious that KVM does indeed
> handle this case.
>
> Note, the double fault case is worded rather wierdly in the SDM:
>
> The original event results in a double-fault exception that causes the
> VM exit directly.
>
> Temporarily ignoring injected events, double faults can _only_ occur if
> an exception occurs while attempting to deliver a different exception,
> i.e. there's _always_ an original event. And for injected double fault,
> while there's no original event, injected events are never subject to
> interception.
>
> Presumably the SDM is calling out that a the vectoring info will be valid
> if a different exit occurs after a double fault, e.g. if a #PF occurs and
> is intercepted while vectoring #DF, then the vectoring info will show the
> double fault.

Wouldn't it be a tripe fault exit in this case?

> In other words, the clause can simply be read as:
>
> The VM exit is caused by a double-fault exception.

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