linux-kernel - Re: [PATCH 3/4] KVM: MMU: reduce the size of mmu_page

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Message-ID: <56F549B0.9040309@redhat.com>
Date:	Fri, 25 Mar 2016 15:22:40 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
Cc:	gleb@...nel.org, mtosatti@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] KVM: MMU: reduce the size of mmu_page_path



On 25/03/2016 15:07, Xiao Guangrong wrote:
>>
>> @@ -2037,13 +2037,14 @@ static void mmu_pages_clear_parents(struct
>> mmu_page_path *parents)
>>   {
>>       struct kvm_mmu_page *sp;
>>       unsigned int level = 0;
>> +    unsigned int idx;
>>
>>       do {
>> -        unsigned int idx = parents->idx[level];
>>           sp = parents->parent[level];
>> -        if (!sp)
>> +        if (!sp || WARN_ON(level == PT64_ROOT_LEVEL-1))
>>               return;
>>
>> +        idx = parents->idx[level];
>>           WARN_ON(idx == INVALID_INDEX);
>>           clear_unsync_child_bit(sp, idx);
>>           level++;
>>
> 
> Yes, exactly.
> 
> [ actually, we can keep mmu_pages_clear_parents() unchanged ]

You cannot because ubsan would complain. :)

Paolo