linux-kernel - Re: [PATCH v2 5/7] KVM: handle more completed apfs if possible

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Message-ID: <20101101092457.GY26191@redhat.com>
Date:	Mon, 1 Nov 2010 11:24:57 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 5/7] KVM: handle more completed apfs if possible

On Mon, Nov 01, 2010 at 05:02:35PM +0800, Xiao Guangrong wrote:
> If it's no need to inject async #PF to PV guest we can handle
> more completed apfs at one time, so we can retry guest #PF
> as early as possible
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> ---
>  arch/x86/include/asm/kvm_host.h |    3 ++-
>  arch/x86/kvm/x86.c              |    8 ++++++--
>  virt/kvm/async_pf.c             |   28 ++++++++++++++++------------
>  3 files changed, 24 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 1be0058..c95b3ff 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -818,7 +818,8 @@ bool kvm_is_linear_rip(struct kvm_vcpu *vcpu, unsigned long linear_rip);
>  
>  void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
>  				     struct kvm_async_pf *work);
> -void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
> +/* return true if we can handle more completed apfs, false otherwise */
> +bool kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
>  				 struct kvm_async_pf *work);
>  void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu,
>  			       struct kvm_async_pf *work);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4da8485..189664a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6265,7 +6265,7 @@ void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
>  	}
>  }
>  
> -void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
> +bool kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
>  				 struct kvm_async_pf *work)
>  {
>  	trace_kvm_async_pf_ready(work->arch.token, work->gva);
> @@ -6274,13 +6274,17 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
>  	else
>  		kvm_del_async_pf_gfn(vcpu, work->arch.gfn);
>  
> +	vcpu->arch.apf.halted = false;
> +
>  	if ((vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED) &&
>  	    !apf_put_user(vcpu, KVM_PV_REASON_PAGE_READY)) {
>  		vcpu->arch.fault.error_code = 0;
>  		vcpu->arch.fault.address = work->arch.token;
>  		kvm_inject_page_fault(vcpu);
> +		return false;
>  	}
> -	vcpu->arch.apf.halted = false;
> +
> +	return true;
>  }
>  
>  bool kvm_arch_can_inject_async_page_present(struct kvm_vcpu *vcpu)
> diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
> index 60df9e0..d57ec92 100644
> --- a/virt/kvm/async_pf.c
> +++ b/virt/kvm/async_pf.c
> @@ -123,25 +123,29 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
>  void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_async_pf *work;
> +	bool ret;
>  
>  	if (list_empty_careful(&vcpu->async_pf.done) ||
>  	    !kvm_arch_can_inject_async_page_present(vcpu))
>  		return;
>  
> -	spin_lock(&vcpu->async_pf.lock);
> -	work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link);
> -	list_del(&work->link);
> -	spin_unlock(&vcpu->async_pf.lock);
> +	do {
> +		spin_lock(&vcpu->async_pf.lock);
> +		work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
> +							link);
> +		list_del(&work->link);
> +		spin_unlock(&vcpu->async_pf.lock);
>  
> -	if (work->page)
> -		kvm_arch_async_page_ready(vcpu, work);
> -	kvm_arch_async_page_present(vcpu, work);
> +		if (work->page)
> +			kvm_arch_async_page_ready(vcpu, work);
> +		ret = kvm_arch_async_page_present(vcpu, work);
>  
> -	list_del(&work->queue);
> -	vcpu->async_pf.queued--;
> -	if (work->page)
> -		put_page(work->page);
> -	kmem_cache_free(async_pf_cache, work);
> +		list_del(&work->queue);
> +		vcpu->async_pf.queued--;
> +		if (work->page)
> +			put_page(work->page);
> +		kmem_cache_free(async_pf_cache, work);
> +	} while (ret && !list_empty_careful(&vcpu->async_pf.done));
>  }
>  
No need to change kvm_arch_async_page_present() to return anything. You
can do while loop like this:

while (!list_empty_careful(&vcpu->async_pf.done) &&
       kvm_arch_can_inject_async_page_present(vcpu)) {
}

If kvm_arch_async_page_present() call injects exception
kvm_arch_can_inject_async_page_present() will return false on next
iteration.

--
			Gleb.
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