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    SubjectRe: [PART1 RFC 5/9] svm: Add VMEXIT handlers for AVIC
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    Hi

    On 02/19/2016 12:18 AM, Paolo Bonzini wrote:
    >
    >
    > On 18/02/2016 17:27, Radim Krčmář wrote:
    >> 2016-02-18 16:53+0100, Paolo Bonzini:
    >>> Patch 9 is okay, but it is also necessary to clear IsRunning in
    >>> kvm_arch_vcpu_blocking and set it in kvm_arch_vcpu_unblocking. In
    >>> addition, vcpu_put/vcpu_load should not modify IsRunning between
    >>> kvm_arch_vcpu_blocking and kvm_arch_vcpu_unblocking. Do you agree?
    >>
    >> Yes.
    >>
    >> I think we don't need to clear IsRunning on preemption, which would
    >> simplify the protection. (I haven't thought much about userspace exit,
    >> so maybe we could skip that one as well, but we don't need to now.)
    >>
    >> The reason for that is that KVM knows that the VCPU was scheduled out,
    >> so it couldn't do much in the AVIC VMEXIT.
    >> (KVM could force scheduler to pritioritize the VCPU, but our kick
    >> doesn't do that now and it seems like a bad idea.)
    >>
    >> Does it seem reasonable?
    >
    > Yes, and in fact it wouldn't need to clear and set IsRunning on
    > vcpu_put/vcpu_load; only on vcpu_blocking/vcpu_unblocking.
    >
    > The IsRunning flag is more of a IsNotHalted flag, in the end.
    >
    > Paolo
    >

    In facts, instead of setting up the vAPIC backing page address when
    calling kvm_arch_vcpu_load(), we should be able to do it when calling
    kvm_arch_vcpu_sched_in(). This seems more appropriate since the
    kvm_arch_vcpu_load() is also called in many unnecessary occasions via
    vcpu_load() (in the arch/x86/kvm/x86.c). The same goes for the
    kvm_arch_vcpu_put().

    However, there is no kvm_arch_vcpu_sched_out(). But that can be added
    easily.

    What do you think?

    Suravee



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