Re: [Xen-devel] [xen-unstable test] 104131: regressions - FAIL

["Xuquan (Quan Xu)" <xuquan8@xxxxxxxxxx>]

On January 18, 2017 5:38 PM, Jan Beulich wrote:
>>>> On 18.01.17 at 05:57, <kevin.tian@xxxxxxxxx> wrote:
>> Attached was my earlier comment:
>>
>> --
>>> >>> On 20.12.16 at 06:37, <kevin.tian@xxxxxxxxx> wrote:
>>> >>  From: Xuquan (Quan Xu) [mailto:xuquan8@xxxxxxxxxx]
>>> >> Sent: Friday, December 16, 2016 5:40 PM
>>> >> -        if (pt_vector != -1)
>>> >> -            vmx_set_eoi_exit_bitmap(v, pt_vector);
>>> >> +        if ( pt_vector != -1 ) {
>>> >> +            if ( intack.vector > pt_vector )
>>> >> +                vmx_set_eoi_exit_bitmap(v, intack.vector);
>>> >> +            else
>>> >> +                vmx_set_eoi_exit_bitmap(v, pt_vector);
>>> >> +        }
>>> >
>>> > Above can be simplified as one line change:
>>> >   if ( pt_vector != -1 )
>>> >           vmx_set_eoi_exit_bitmap(v, intack.vector);
>>>
>>> Hmm, I don't understand. Did you mean to use max() here? Or else how
>>> is this an equivalent of the originally proposed code?
>>>
>>
>> Original code is not 100% correct. The purpose is to set EOI exit
>> bitmap for any vector which may block injection of pt_vector - give
>> chance to recognize pt_vector in future intack and then do pt intr
>> post. The simplified code achieves this effect same as original code
>> if intack.vector >= vector. I cannot come up a case why intack.vector
>> might be smaller than vector. If this case happens, we still need
>> enable exit bitmap for intack.vector instead of pt_vector for said
>> purpose while original code did it wrong.
>>
>> Thanks
>> Kevin
>> --
>>
>> Using intack.vector is always expected here regardless of the
>> comparison result between intack.vector and pt_vector. The reason why
>> I was OK adding an ASSERT was simply to test whether
>> intack.vecor<pt_vector does happen which is orthogonal to the fix
>> itself.
>
>Well, a vector lower than pt_vector can't block delivery. Or wait:
>Don't we need to consider vector classes here, i.e.
>
>            ASSERT((intack.vector >> 4) >= (pt_vector >> 4));
>

Jan, I can't follow vector classes.. could you explain more? Thanks..


Quan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel