linux-kernel - Re: [PATCH v2 1/5] KVM: MMU: release noslot pfn on the fail path properly

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Date:	Sat, 15 Sep 2012 12:13:38 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	Avi Kivity <avi@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
	KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] KVM: MMU: release noslot pfn on the fail path
 properly

On Fri, Sep 14, 2012 at 05:57:22PM +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
> 
> 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(-)

Its clearer to the reader if is_invalid_pfn() is used instead of 
is_error_pfn.

BTW how about killing this unused helper

static bool mmu_invalid_pfn(pfn_t pfn)
{
        return unlikely(is_invalid_pfn(pfn));
}

This can be done inlined.

> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index aa0b469..f74c63a 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 (!is_error_pfn(pfn))
> +		kvm_release_pfn_clean(pfn);
>  	return 0;
>  }

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