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    Subject[PATCH 1/3] KVM: LAPIC: Make lapic timer unpinned when timer is injected by posted-interrupt
    Date
    From: Wanpeng Li <wanpengli@tencent.com>

    Make lapic timer unpinned when timer is injected by posted-interrupt,
    the emulated timer can be offload to the housekeeping cpus.

    This patch introduces a new kvm module parameter, it is false by default.
    The host admin can enable it after fine tuned, e.g. dedicated instances
    scenario w/ nohz_full cover the pCPUs which vCPUs resident, several pCPUs
    surplus for housekeeping, disable mwait/hlt/pause vmexits to occupy the
    pCPUs, fortunately preemption timer is disabled after mwait is exposed
    to guest which makes emulated timer offload can be possible.

    Cc: Paolo Bonzini <pbonzini@redhat.com>
    Cc: Radim Krčmář <rkrcmar@redhat.com>
    Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
    ---
    arch/x86/include/asm/kvm_host.h | 1 +
    arch/x86/kvm/lapic.c | 20 ++++++++++++++++----
    arch/x86/kvm/svm.c | 5 +++++
    arch/x86/kvm/vmx/vmx.c | 9 +++++++++
    4 files changed, 31 insertions(+), 4 deletions(-)

    diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    index aeadbc7..ccb3d61 100644
    --- a/arch/x86/include/asm/kvm_host.h
    +++ b/arch/x86/include/asm/kvm_host.h
    @@ -1090,6 +1090,7 @@ struct kvm_x86_ops {
    void (*set_virtual_apic_mode)(struct kvm_vcpu *vcpu);
    void (*set_apic_access_page_addr)(struct kvm_vcpu *vcpu, hpa_t hpa);
    void (*deliver_posted_interrupt)(struct kvm_vcpu *vcpu, int vector);
    + bool (*pi_inject_timer_enabled)(struct kvm_vcpu *vcpu);
    int (*sync_pir_to_irr)(struct kvm_vcpu *vcpu);
    int (*set_tss_addr)(struct kvm *kvm, unsigned int addr);
    int (*set_identity_map_addr)(struct kvm *kvm, u64 ident_addr);
    diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
    index fcf42a3..8c9c14d 100644
    --- a/arch/x86/kvm/lapic.c
    +++ b/arch/x86/kvm/lapic.c
    @@ -127,6 +127,12 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic)
    return apic->vcpu->vcpu_id;
    }

    +static inline bool posted_interrupt_inject_timer(struct kvm_vcpu *vcpu)
    +{
    + return (kvm_x86_ops->pi_inject_timer_enabled(vcpu) &&
    + kvm_mwait_in_guest(vcpu->kvm));
    +}
    +
    static inline bool kvm_apic_map_get_logical_dest(struct kvm_apic_map *map,
    u32 dest_id, struct kvm_lapic ***cluster, u16 *mask) {
    switch (map->mode) {
    @@ -1581,7 +1587,9 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
    likely(ns > apic->lapic_timer.timer_advance_ns)) {
    expire = ktime_add_ns(now, ns);
    expire = ktime_sub_ns(expire, ktimer->timer_advance_ns);
    - hrtimer_start(&ktimer->timer, expire, HRTIMER_MODE_ABS_PINNED);
    + hrtimer_start(&ktimer->timer, expire,
    + posted_interrupt_inject_timer(vcpu) ?
    + HRTIMER_MODE_ABS : HRTIMER_MODE_ABS_PINNED);
    } else
    apic_timer_expired(apic);

    @@ -1683,7 +1691,8 @@ static void start_sw_period(struct kvm_lapic *apic)

    hrtimer_start(&apic->lapic_timer.timer,
    apic->lapic_timer.target_expiration,
    - HRTIMER_MODE_ABS_PINNED);
    + posted_interrupt_inject_timer(apic->vcpu) ?
    + HRTIMER_MODE_ABS : HRTIMER_MODE_ABS_PINNED);
    }

    bool kvm_lapic_hv_timer_in_use(struct kvm_vcpu *vcpu)
    @@ -2320,7 +2329,8 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns)
    apic->vcpu = vcpu;

    hrtimer_init(&apic->lapic_timer.timer, CLOCK_MONOTONIC,
    - HRTIMER_MODE_ABS_PINNED);
    + posted_interrupt_inject_timer(vcpu) ?
    + HRTIMER_MODE_ABS : HRTIMER_MODE_ABS_PINNED);
    apic->lapic_timer.timer.function = apic_timer_fn;
    if (timer_advance_ns == -1) {
    apic->lapic_timer.timer_advance_ns = 1000;
    @@ -2509,7 +2519,9 @@ void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)

    timer = &vcpu->arch.apic->lapic_timer.timer;
    if (hrtimer_cancel(timer))
    - hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
    + hrtimer_start_expires(timer,
    + posted_interrupt_inject_timer(vcpu) ?
    + HRTIMER_MODE_ABS : HRTIMER_MODE_ABS_PINNED);
    }

    /*
    diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
    index 302cb40..aee1d91 100644
    --- a/arch/x86/kvm/svm.c
    +++ b/arch/x86/kvm/svm.c
    @@ -5173,6 +5173,11 @@ static void svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec)
    kvm_vcpu_wake_up(vcpu);
    }

    +static inline bool svm_posted_interrupt_inject_timer(struct kvm_vcpu *vcpu)
    +{
    + return false;
    +}
    +
    static void svm_ir_list_del(struct vcpu_svm *svm, struct amd_iommu_pi_data *pi)
    {
    unsigned long flags;
    diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
    index da24f18..2b4fd61 100644
    --- a/arch/x86/kvm/vmx/vmx.c
    +++ b/arch/x86/kvm/vmx/vmx.c
    @@ -101,6 +101,9 @@ module_param(fasteoi, bool, S_IRUGO);
    static bool __read_mostly enable_apicv = 1;
    module_param(enable_apicv, bool, S_IRUGO);

    +bool __read_mostly pi_inject_timer = 0;
    +module_param(pi_inject_timer, bool, S_IRUGO);
    +
    /*
    * If nested=1, nested virtualization is supported, i.e., guests may use
    * VMX and be a hypervisor for its own guests. If nested=0, guests may not
    @@ -3724,6 +3727,11 @@ static void vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu, int vector)
    kvm_vcpu_kick(vcpu);
    }

    +static bool vmx_pi_inject_timer_enabled(struct kvm_vcpu *vcpu)
    +{
    + return pi_inject_timer && kvm_vcpu_apicv_active(vcpu);
    +}
    +
    /*
    * Set up the vmcs's constant host-state fields, i.e., host-state fields that
    * will not change in the lifetime of the guest.
    @@ -7671,6 +7679,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
    .guest_apic_has_interrupt = vmx_guest_apic_has_interrupt,
    .sync_pir_to_irr = vmx_sync_pir_to_irr,
    .deliver_posted_interrupt = vmx_deliver_posted_interrupt,
    + .pi_inject_timer_enabled = vmx_pi_inject_timer_enabled,

    .set_tss_addr = vmx_set_tss_addr,
    .set_identity_map_addr = vmx_set_identity_map_addr,
    --
    2.7.4
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