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


    On 19/12/2014 02:30, Wu, Feng wrote:
    >>> 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
    >
    > Paolo, what do you mean by "single-CPU interrupts"? Do you mean we don't
    > support lowest priority interrupts for PI? But Linux OS uses lowest priority
    > for most of the case? If so, we can hardly get benefit from this feature for
    > Linux guest OS.

    You can post lowest priority interrupts if they are delivered to a
    single CPU, in which case they are effectively fixed priority.

    If they are broadcast to multiple CPUs, do not post them.

    Paolo


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