linux-kernel - Re: [PATCH 2/2] KVM: MMU: allow more page become unsync at getting sp time

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Message-ID: <4BFA1BD9.5070302@redhat.com>
Date:	Mon, 24 May 2010 09:25:29 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH 2/2] KVM: MMU: allow more page become unsync at getting
 sp time

On 05/24/2010 05:31 AM, Xiao Guangrong wrote:
>
> Avi Kivity wrote:
>    
>> On 05/23/2010 03:16 PM, Xiao Guangrong wrote:
>>      
>>> Allow more page become asynchronous at getting sp time, if need create
>>> new
>>> shadow page for gfn but it not allow unsync(level>   1), we should
>>> unsync all
>>> gfn's unsync page
>>>
>>>
>>>
>>> +/* @gfn should be write-protected at the call site */
>>> +static void kvm_sync_pages(struct kvm_vcpu *vcpu,  gfn_t gfn)
>>> +{
>>> +    struct hlist_head *bucket;
>>> +    struct kvm_mmu_page *s;
>>> +    struct hlist_node *node, *n;
>>> +    unsigned index;
>>> +    bool flush = false;
>>> +
>>> +    index = kvm_page_table_hashfn(gfn);
>>> +    bucket =&vcpu->kvm->arch.mmu_page_hash[index];
>>> +    hlist_for_each_entry_safe(s, node, n, bucket, hash_link) {
>>>
>>>        
>> role.direct, role.invalid?
>>      
> We only handle unsync pages here, and 'role.direct' or 'role.invalid'
> pages can't become unsync.
>    

They will be once the invlpg patch is in...

>    
>> Well, role.direct cannot be unsync.  But that's not something we want to
>> rely on.
>>      
> While we mark the unsync page, we have filtered out the 'role.direct' pages,
> so, i think we not need worry 'role.direct' here. :-)
>    

Ok.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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