Re: [PATCH 3/4] KVM: MMU: reduce the size of mmu_page_path

[Paolo Bonzini]

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