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    SubjectRe: [v3 13/26] KVM: Define a new interface kvm_find_dest_vcpu() for VT-d PI


    On 18/12/2014 15:49, Zhang, Yang Z wrote:
    >>> Here, we introduce a similar way with 'apic_arb_prio' to handle
    >>> guest lowest priority interrtups when VT-d PI is used. Here is
    >>> the ideas: - Each vCPU has a counter 'round_robin_counter'. -
    >>> When guests sets an interrupts to lowest priority, we choose the
    >>> vCPU with smallest 'round_robin_counter' as the destination, then
    >>> increase it.
    >
    > How this can work well? All subsequent interrupts are delivered to
    > one vCPU? It shouldn't be the best solution, need more consideration.

    Well, it's a hardware limitation. The alternative (which is easy to
    implement) is to only do PI for single-CPU interrupts. This should work
    well for multiqueue NICs (and of course for UP guests :)), so perhaps
    it's a good idea to only support that as a first attempt.

    Paolo

    > Also, I think you should take the apic_arb_prio into consider since
    > the priority is for the whole vCPU not for one interrupt.


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