Re: Is this a data corruption bug for p2m_ram_shared page in hvm_hap_nested_page_fault()

["nai.xia" <nai.xia@gmail.com>]

On 2012年02月02日 19:19, Tim Deegan wrote:
> At 18:25 +0800 on 02 Feb (1328207143), nai.xia wrote:
>> On 2012???02???02??? 18:17, nai.xia wrote:
>>> In hvm_hap_nested_page_fault(), it seems that all valid write faults are
>>> now handled
>>> by p2m_mem_access_check(), right? Then when will mem_sharing_unshare_page()
>>> be called? And if p2m->access_required == false, the access restrictions
>>> is cleared
>>
>> Oh, sorry, I notice that with p2m_ram_shared, the write permissions is
>> always cleared.  But, still, this seems cannot lead to the call of
>> mem_sharing_unshare_page() and this write fault will happen again and
>> again?
>
> There's an explicit call of mem_sharing_unshare_page() in
> hvm_hap_nested_page_fault(); the only thing that will skip that is if
> the fault is caused by a p2m_access violation, in which case
> we report the fault on the p2m_access ring and wait for the consumer of
> that ring to fix the problem.

Oh, yes! I was mistaken that the write flag of p2m_access would also be
removed for p2m_ram_shared pages just like entry->w in ept_set_entry().
I am clear about the role of the p2m_access_t now.

Thanks for the reply! :)


Regards,

Nai

>
> Cheers,
>
> Tim.

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