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Date: Thu, 24 Oct 2013 18:10:46 +0800
From: Xiao Guangrong <xiaoguangrong.eric@gmail.com>
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To: Gleb Natapov <gleb@redhat.com>,
        Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
CC: avi.kivity@gmail.com, mtosatti@redhat.com, pbonzini@redhat.com,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v3 10/15] KVM: MMU: allocate shadow pages from slab
References: <1382534973-13197-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <1382534973-13197-11-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <20131024091905.GB5289@redhat.com> <5268E888.7060608@linux.vnet.ibm.com> <20131024095204.GD5289@redhat.com>
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On 10/24/2013 05:52 PM, Gleb Natapov wrote:
> On Thu, Oct 24, 2013 at 05:29:44PM +0800, Xiao Guangrong wrote:
>> On 10/24/2013 05:19 PM, Gleb Natapov wrote:
>>
>>>> @@ -946,7 +947,7 @@ static inline struct kvm_mmu_page *page_header(hpa_t shadow_page)
>>>>  {
>>>>  	struct page *page = pfn_to_page(shadow_page >> PAGE_SHIFT);
>>>>  
>>>> -	return (struct kvm_mmu_page *)page_private(page);
>>>> +	return (struct kvm_mmu_page *)(page->mapping);
>>> Why?
>>
>> That's because page->private has been used by slab:
>>
> But does lockless path actually looks at it?

Lockless path does not use it, however, it is used by kvm_mmu_page():

static inline struct kvm_mmu_page *page_header(hpa_t shadow_page)
{
	struct page *page = pfn_to_page(shadow_page >> PAGE_SHIFT);

	return (struct kvm_mmu_page *)(page->mapping);
}

which is used in the common code.