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    Subject[PATCH RFC V2 1/2] kvm vcpu: Note down pause loop exit
    From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>

    Noting pause loop exited vcpu helps in filtering right candidate to yield.
    Yielding to same vcpu may result in more wastage of cpu.

    Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
    ---

    arch/x86/include/asm/kvm_host.h | 11 +++++++++++
    arch/x86/kvm/svm.c | 1 +
    arch/x86/kvm/vmx.c | 1 +
    arch/x86/kvm/x86.c | 4 +++-
    4 files changed, 16 insertions(+), 1 deletions(-)


    diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    index db7c1f2..386f3e6 100644
    --- a/arch/x86/include/asm/kvm_host.h
    +++ b/arch/x86/include/asm/kvm_host.h
    @@ -484,6 +484,17 @@ struct kvm_vcpu_arch {
    u64 length;
    u64 status;
    } osvw;
    +
    + /*
    + * Pause loop exit optimization
    + * pause_loop_exited: set when a vcpu does a pause loop exit.
    + * dy_eligible: indicates whether vcpu is eligible for directed yield.
    + */
    + struct {
    + bool pause_loop_exited;
    + bool dy_eligible;
    + } ple;
    +
    };

    struct kvm_lpage_info {
    diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
    index f75af40..2b4b4ee 100644
    --- a/arch/x86/kvm/svm.c
    +++ b/arch/x86/kvm/svm.c
    @@ -3264,6 +3264,7 @@ static int interrupt_window_interception(struct vcpu_svm *svm)

    static int pause_interception(struct vcpu_svm *svm)
    {
    + svm->vcpu.arch.ple.pause_loop_exited = true;
    kvm_vcpu_on_spin(&(svm->vcpu));
    return 1;
    }
    diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
    index 32eb588..14aa67a 100644
    --- a/arch/x86/kvm/vmx.c
    +++ b/arch/x86/kvm/vmx.c
    @@ -4945,6 +4945,7 @@ out:
    static int handle_pause(struct kvm_vcpu *vcpu)
    {
    skip_emulated_instruction(vcpu);
    + vcpu->arch.ple.pause_loop_exited = true;
    kvm_vcpu_on_spin(vcpu);

    return 1;
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index be6d549..b30c310 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -5331,7 +5331,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)

    if (req_immediate_exit)
    smp_send_reschedule(vcpu->cpu);
    -
    + vcpu->arch.ple.pause_loop_exited = false;
    kvm_guest_enter();

    if (unlikely(vcpu->arch.switch_db_regs)) {
    @@ -6168,6 +6168,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
    BUG_ON(vcpu->kvm == NULL);
    kvm = vcpu->kvm;

    + vcpu->arch.ple.pause_loop_exited = false;
    + vcpu->arch.ple.dy_eligible = false;
    vcpu->arch.emulate_ctxt.ops = &emulate_ops;
    if (!irqchip_in_kernel(kvm) || kvm_vcpu_is_bsp(vcpu))
    vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;


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