Re: [PATCH 2/5] KVM: x86: do not scan IRR twice on APICv vmentry

[Wanpeng Li]

2016-10-15 2:21 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>:
> Calling apic_find_highest_irr results in IRR being scanned twice,
> once in vmx_sync_pir_from_irr and once in apic_search_irr.  Change

s/from/to

> sync_pir_from_irr to do the RVI write and kvm_apic_update_irr to
> compute the new RVI on the fly.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
>  arch/x86/kvm/lapic.c | 25 +++++++++++++++++--------
>  arch/x86/kvm/lapic.h |  4 ++--
>  arch/x86/kvm/vmx.c   | 24 +++++++++++++-----------
>  arch/x86/kvm/x86.c   |  3 +--
>  4 files changed, 33 insertions(+), 23 deletions(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 63a442aefc12..a24492a88643 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -317,7 +317,7 @@ static int find_highest_vector(void *bitmap)
>              vec >= 0; vec -= APIC_VECTORS_PER_REG) {
>                 reg = bitmap + REG_POS(vec);
>                 if (*reg)
> -                       return fls(*reg) - 1 + vec;
> +                       return __fls(*reg) + vec;
>         }
>
>         return -1;
> @@ -337,27 +337,36 @@ static u8 count_vectors(void *bitmap)
>         return count;
>  }
>
> -void __kvm_apic_update_irr(u32 *pir, void *regs)
> +int __kvm_apic_update_irr(u32 *pir, void *regs)
>  {
> -       u32 i, pir_val;
> +       u32 i, vec;
> +       u32 pir_val, irr_val;
> +       int max_irr = -1;
>
> -       for (i = 0; i <= 7; i++) {
> +       for (i = vec = 0; i <= 7; i++, vec += 32) {
>                 pir_val = READ_ONCE(pir[i]);
> +               irr_val = *((u32 *)(regs + APIC_IRR + i * 0x10));
>                 if (pir_val) {
> -                       pir_val = xchg(&pir[i], 0);
> -                       *((u32 *)(regs + APIC_IRR + i * 0x10)) |= pir_val;
> +                       irr_val |= xchg(&pir[i], 0);
> +                       *((u32 *)(regs + APIC_IRR + i * 0x10)) = irr_val;
>                 }
> +               if (irr_val)
> +                       max_irr = __fls(irr_val) + vec;
>         }
> +
> +       return max_irr;
>  }
>  EXPORT_SYMBOL_GPL(__kvm_apic_update_irr);
>
> -void kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir)
> +int kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir)
>  {
>         struct kvm_lapic *apic = vcpu->arch.apic;
> +       int max_irr;
>
> -       __kvm_apic_update_irr(pir, apic->regs);
> +       max_irr = __kvm_apic_update_irr(pir, apic->regs);
>
>         kvm_make_request(KVM_REQ_EVENT, vcpu);
> +       return max_irr;
>  }
>  EXPORT_SYMBOL_GPL(kvm_apic_update_irr);
>
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index f60d01c29d51..fc72828c3782 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -70,8 +70,8 @@ int kvm_lapic_reg_read(struct kvm_lapic *apic, u32 offset, int len,
>  bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
>                            int short_hand, unsigned int dest, int dest_mode);
>
> -void __kvm_apic_update_irr(u32 *pir, void *regs);
> -void kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir);
> +int __kvm_apic_update_irr(u32 *pir, void *regs);
> +int kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir);
>  int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
>                      struct dest_map *dest_map);
>  int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type);
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 7c79d6c6b6ed..c985ec8736d3 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -4856,17 +4856,6 @@ static void vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu, int vector)
>                 kvm_vcpu_kick(vcpu);
>  }
>
> -static void vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
> -{
> -       struct vcpu_vmx *vmx = to_vmx(vcpu);
> -
> -       if (!pi_test_on(&vmx->pi_desc))
> -               return;
> -
> -       pi_clear_on(&vmx->pi_desc);
> -       kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
> -}
> -
>  /*
>   * Set up the vmcs's constant host-state fields, i.e., host-state fields that
>   * will not change in the lifetime of the guest.
> @@ -8613,6 +8602,19 @@ static void vmx_hwapic_irr_update(struct kvm_vcpu *vcpu, int max_irr)
>         }
>  }
>
> +static void vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
> +{
> +       struct vcpu_vmx *vmx = to_vmx(vcpu);
> +       int max_irr;
> +
> +       if (!pi_test_on(&vmx->pi_desc))
> +               return;
> +
> +       pi_clear_on(&vmx->pi_desc);
> +       max_irr = kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
> +       vmx_hwapic_irr_update(vcpu, max_irr);
> +}
> +
>  static void vmx_load_eoi_exitmap(struct kvm_vcpu *vcpu, u64 *eoi_exit_bitmap)
>  {
>         if (!kvm_vcpu_apicv_active(vcpu))
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3ee8a91a78c3..3d29be9d9db4 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6611,8 +6611,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>                  * virtual interrupt delivery.
>                  */
>                 if (vcpu->arch.apicv_active)
> -                       kvm_x86_ops->hwapic_irr_update(vcpu,
> -                               kvm_lapic_find_highest_irr(vcpu));
> +                       kvm_x86_ops->sync_pir_to_irr(vcpu);
>         }
>
>         if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
> --
> 1.8.3.1
>
>
> --
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