Re: [PATCH] mm: mmu_notifier: fix inconsistent memory between secondary MMU and host

Xiao Guangrong
2012-08-22T05:38:10Z

On 08/22/2012 12:12 PM, Hugh Dickins wrote:
> On Wed, 22 Aug 2012, Xiao Guangrong wrote:
>> On 08/21/2012 11:06 PM, Andrea Arcangeli wrote:
>>>
>>> The KSM usage of it looks safe because it will only establish readonly
>>> ptes with it.
>>
>> Hmm, in KSM code, i found this code in replace_page:
>>
>> set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
>>
>> It is possible to establish a writable pte, no?
>
> No: we only do KSM in private vmas (!VM_SHARED), and because of the
> need to CopyOnWrite in those, vm_page_prot excludes write permission:
> write permission has to be added on COW fault.

After read the code carefully, yes, you are right. Thank you very much
for your explanation, Hugh! :)