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From: Paolo Bonzini <pbonzini@redhat.com>
To: Wanpeng Li <kernellwp@gmail.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH v2 5/9] KVM: LAPIC: Narrow down the kick target vCPU
Date: Sat, 12 Sep 2020 08:46:15 +0200	[thread overview]
Message-ID: <9281f28a-e2bd-a79c-fc94-4999f4c6307a@redhat.com> (raw)
In-Reply-To: <1599731444-3525-6-git-send-email-wanpengli@tencent.com>

On 10/09/20 11:50, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
> 
> The kick after setting KVM_REQ_PENDING_TIMER is used to handle the timer
> fires on a different pCPU which vCPU is running on, this kick is expensive
> since memory barrier, rcu, preemption disable/enable operations. We don't
> need this kick when injecting already-expired timer, we also should call
> out the VMX preemption timer case, which also passes from_timer_fn=false
> but doesn't need a kick because kvm_lapic_expired_hv_timer() is called
> from the target vCPU.
> 
> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
>  arch/x86/kvm/lapic.c | 4 +++-
>  arch/x86/kvm/x86.c   | 6 ------
>  arch/x86/kvm/x86.h   | 1 -
>  3 files changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index e446bdf..3b32d3b 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1642,7 +1642,9 @@ static void apic_timer_expired(struct kvm_lapic *apic, bool from_timer_fn)
>  	}
>  
>  	atomic_inc(&apic->lapic_timer.pending);
> -	kvm_set_pending_timer(vcpu);
> +	kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
> +	if (from_timer_fn)
> +		kvm_vcpu_kick(vcpu);
>  }

This only matters for !APICv, but it's nice anyway.

Paolo

>  static void start_sw_tscdeadline(struct kvm_lapic *apic)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d39d6cf..dcf4494 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1774,12 +1774,6 @@ static s64 get_kvmclock_base_ns(void)
>  }
>  #endif
>  
> -void kvm_set_pending_timer(struct kvm_vcpu *vcpu)
> -{
> -	kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
> -	kvm_vcpu_kick(vcpu);
> -}
> -
>  static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
>  {
>  	int version;
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 995ab69..ea20b8b 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -246,7 +246,6 @@ static inline bool kvm_vcpu_latch_init(struct kvm_vcpu *vcpu)
>  	return is_smm(vcpu) || kvm_x86_ops.apic_init_signal_blocked(vcpu);
>  }
>  
> -void kvm_set_pending_timer(struct kvm_vcpu *vcpu);
>  void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);
>  
>  void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr);
> 


  reply	other threads:[~2020-09-12  6:46 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-10  9:50 [PATCH v2 0/9] KVM: collect sporadic patches Wanpeng Li
2020-09-10  9:50 ` [PATCH v2 1/9] KVM: LAPIC: Return 0 when getting the tscdeadline timer if the lapic is hw disabled Wanpeng Li
2020-09-10  9:50 ` [PATCH v2 2/9] KVM: LAPIC: Guarantee the timer is in tsc-deadline mode when setting Wanpeng Li
2020-09-10  9:50 ` [PATCH v2 3/9] KVM: LAPIC: Fix updating DFR missing apic map recalculation Wanpeng Li
2020-09-10  9:50 ` [PATCH v2 4/9] KVM: VMX: Don't freeze guest when event delivery causes an APIC-access exit Wanpeng Li
2020-09-29 21:42   ` Jim Mattson
2020-09-10  9:50 ` [PATCH v2 5/9] KVM: LAPIC: Narrow down the kick target vCPU Wanpeng Li
2020-09-12  6:46   ` Paolo Bonzini [this message]
2020-09-10  9:50 ` [PATCH v2 6/9] KVM: LAPIC: Reduce world switch latency caused by timer_advance_ns Wanpeng Li
2020-09-10  9:50 ` [PATCH v2 7/9] KVM: SVM: Get rid of handle_fastpath_set_msr_irqoff() Wanpeng Li
2020-09-10  9:50 ` [PATCH v2 8/9] KVM: SVM: Move svm_complete_interrupts() into svm_vcpu_run() Wanpeng Li
2020-09-10  9:50 ` [PATCH v2 9/9] KVM: SVM: Reenable handle_fastpath_set_msr_irqoff() after complete_interrupts() Wanpeng Li
2020-09-12  6:47 ` [PATCH v2 0/9] KVM: collect sporadic patches Paolo Bonzini

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