linux-kernel - Re: [PATCH v3 16/19] KVM: MMU: lockless walking shadow page table

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Date:	Thu, 07 Jul 2011 03:26:14 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
CC:	Avi Kivity <avi@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
	KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v3 16/19] KVM: MMU: lockless walking shadow page table

On 07/07/2011 02:08 AM, Marcelo Tosatti wrote:

>> +static void free_pages_rcu(struct rcu_head *head)
>> +{
>> +	struct kvm_mmu_page *next, *sp;
>> +
>> +	sp = container_of(head, struct kvm_mmu_page, rcu);
>> +	while (sp) {
>> +		if (!list_empty(&sp->link))
>> +			next = list_first_entry(&sp->link,
>> +				      struct kvm_mmu_page, link);
>> +		else
>> +			next = NULL;
>> +		kvm_mmu_free_page(sp);
>> +		sp = next;
>> +	}
>> +}
> 
> There is no need for this while loop.
> 

The while loop is needed, since many shadow pages can be freed together in
the rcu context, on commit_zap_page path, we only remove the list head, and
the shadow page is still listed.

 

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