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    Subject[PATCH 05/35] KVM: introduce kvm_vcpu_on_spin
    Date
    From: Zhai, Edwin <edwin.zhai@intel.com>

    Introduce kvm_vcpu_on_spin, to be used by VMX/SVM to yield processing
    once the cpu detects pause-based looping.

    Signed-off-by: "Zhai, Edwin" <edwin.zhai@intel.com>
    Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
    ---
    include/linux/kvm_host.h | 1 +
    virt/kvm/kvm_main.c | 15 +++++++++++++++
    2 files changed, 16 insertions(+), 0 deletions(-)

    diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
    index b985a29..bd5a616 100644
    --- a/include/linux/kvm_host.h
    +++ b/include/linux/kvm_host.h
    @@ -286,6 +286,7 @@ int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn);
    void mark_page_dirty(struct kvm *kvm, gfn_t gfn);

    void kvm_vcpu_block(struct kvm_vcpu *vcpu);
    +void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
    void kvm_resched(struct kvm_vcpu *vcpu);
    void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);
    void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);
    diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    index 70c8cbe..cac69c4 100644
    --- a/virt/kvm/kvm_main.c
    +++ b/virt/kvm/kvm_main.c
    @@ -1108,6 +1108,21 @@ void kvm_resched(struct kvm_vcpu *vcpu)
    }
    EXPORT_SYMBOL_GPL(kvm_resched);

    +void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu)
    +{
    + ktime_t expires;
    + DEFINE_WAIT(wait);
    +
    + prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
    +
    + /* Sleep for 100 us, and hope lock-holder got scheduled */
    + expires = ktime_add_ns(ktime_get(), 100000UL);
    + schedule_hrtimeout(&expires, HRTIMER_MODE_ABS);
    +
    + finish_wait(&vcpu->wq, &wait);
    +}
    +EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin);
    +
    static int kvm_vcpu_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
    {
    struct kvm_vcpu *vcpu = vma->vm_file->private_data;
    --
    1.6.5.2


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