Re: [v5][PATCH 1/2] xen:x86:mm:p2m: introduce set_identity_p2m_entry

["Chen, Tiejun" <tiejun.chen@intel.com>]

On 2014/7/29 17:53, Jan Beulich wrote:
>>>> On 29.07.14 at 11:11, <tiejun.chen@intel.com> wrote:
>> On 2014/7/29 16:19, Jan Beulich wrote:
>>> ? Of course it may still be necessary to also inspect the obtained p2mt
>>> and a.
>>>
>>
>> Are you saying this?
>>
>> 	if ( !p2m_is_valid(p2mt) ||
>> 	     !mfn_valid(mfn) ||
>> 	     (a != p2m_access_rw) )
>
> I'm afraid that's not enough context to know whether what you
> mean to do is sufficient. Plus !p2m_is_valid() is too weak. You
> simply need to properly think through what should happen if you
> find a valid mapping, but any of the tuple (mfn, p2mt, a) don't
> match what you intend to be there.
>

Actually as I understand we can create these mapping only in one case of 
!mfn_valid(mfn). For others scenarios we just return with that  warning 
message no matter what that tuple is explicitly. So here I try to 
understand why you're saying we need check more by show this condition 
combination.

Thanks
Tiejun