Re: [Xen-devel] Re: changeset 22526:7a5ee3800417

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

Peng fei,

I just noticed this patch has a bug -- it doesn't set new_entry.mfn if
the new mfn is the same as the one already in ept_entry!  Standby for
a new one...

 -George

On Mon, Mar 7, 2011 at 4:41 PM, George Dunlap
<George.Dunlap@xxxxxxxxxxxxx> wrote:
> Peng fei,
>
> Can you test the attached patch (to xen-unstable)?  I don't have
> EPT-enabled hardware handy...
>
>  -George
>
> On Mon, Mar 7, 2011 at 4:20 PM, George Dunlap <george.dunlap@xxxxxxxxxx> 
> wrote:
>> Hmm, yeah, that's obviously not right!  Let me take a look...
>>
>>  -George
>>
>> On Mon, 2011-03-07 at 09:55 +0000, 张鹏飞 wrote:
>>> Hi,
>>>     Recently, I did a research on the p2m and EPT,and did apply your
>>> patch(22526) to the source code of mine. But there is one place
>>> confused me:
>>>
>>>
>>>
>>> ept_entry = table + index;
>>> 1.91
>>>     1.92 -        ept_entry->emt = epte_get_entry_emt(d, gfn, mfn, &ipat, 
>>> direct_mmio);
>>>     1.93 -        ept_entry->ipat = ipat;
>>>     1.94 -        ept_entry->sp = i ? 1 : 0;
>>>     1.95 -        ept_entry->avail1 = p2mt;
>>>     1.96 -        ept_entry->avail2 = 0;
>>>     1.97 +        new_entry.emt = epte_get_entry_emt(d, gfn, mfn, &ipat, 
>>> direct_mmio);
>>>     1.98 +        new_entry.ipat = ipat;
>>>     1.99 +        new_entry.sp = i ? 1 : 0;
>>>    1.100 +        new_entry.avail1 = p2mt;
>>>    1.101 +        new_entry.avail2 = 0;
>>>    1.102
>>>    1.103 -        if ( ept_entry->mfn == mfn_x(mfn) )
>>>    1.104 +        if ( new_entry.mfn == mfn_x(mfn) )
>>>    1.105               need_modify_vtd_table = 0;
>>>    1.106          else /* the caller should take care of the previous page 
>>> */
>>>    1.107 -            ept_entry->mfn = mfn_x(mfn);
>>>    1.108 +            new_entry.mfn = mfn_x(mfn);
>>>
>>> I think, The new_entry.mfn is used without assigned any value. Maybe there 
>>> was something else I did not think of.
>>> Thank you for your kindness!
>>>
>>> http://xenbits.xen.org/xen-unstable.hg/rev/7a5ee3800417
>>
>>
>>
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>>
>

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