linux-kernel - Re: [PATCH v3 1/7] KVM: MMU: fix release noslot pfn

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Message-ID: <20120923091335.GA20907@redhat.com>
Date:	Sun, 23 Sep 2012 11:13:35 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.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 v3 1/7] KVM: MMU: fix release noslot pfn

On Fri, Sep 21, 2012 at 02:57:19PM +0800, Xiao Guangrong wrote:
> We can not directly call kvm_release_pfn_clean to release the pfn
> since we can meet noslot pfn which is used to cache mmio info into
> spte
> 
Wouldn't it be better to move the check into kvm_release_pfn_clean()?

> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
> ---
>  arch/x86/kvm/mmu.c         |    6 ++++--
>  arch/x86/kvm/paging_tmpl.h |    6 ++++--
>  2 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index aa0b469..0f56169 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2877,7 +2877,8 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, u32 error_code,
> 
>  out_unlock:
>  	spin_unlock(&vcpu->kvm->mmu_lock);
> -	kvm_release_pfn_clean(pfn);
> +	if (likely(!is_noslot_pfn(pfn)))
> +		kvm_release_pfn_clean(pfn);
>  	return 0;
>  }
> 
> @@ -3345,7 +3346,8 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
> 
>  out_unlock:
>  	spin_unlock(&vcpu->kvm->mmu_lock);
> -	kvm_release_pfn_clean(pfn);
> +	if (likely(!is_noslot_pfn(pfn)))
> +		kvm_release_pfn_clean(pfn);
>  	return 0;
>  }
> 
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index bf8c42b..9ce6bc0 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -544,7 +544,8 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
>  out_gpte_changed:
>  	if (sp)
>  		kvm_mmu_put_page(sp, it.sptep);
> -	kvm_release_pfn_clean(pfn);
> +	if (likely(!is_noslot_pfn(pfn)))
> +		kvm_release_pfn_clean(pfn);
>  	return NULL;
>  }
> 
> @@ -645,7 +646,8 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
> 
>  out_unlock:
>  	spin_unlock(&vcpu->kvm->mmu_lock);
> -	kvm_release_pfn_clean(pfn);
> +	if (likely(!is_noslot_pfn(pfn)))
> +		kvm_release_pfn_clean(pfn);
>  	return 0;
>  }
> 
> -- 
> 1.7.7.6
> 
> --
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--
			Gleb.
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