Re: [Xen-devel] Xen mce bugfix

["Liu, Jinsong" <jinsong.liu@xxxxxxxxx>]

Jan Beulich wrote:
>>>> On 27.02.13 at 11:37, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
>> Jan Beulich wrote:
>>>>>> On 27.02.13 at 10:24, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx>
>>>>>> wrote: 
>>>> This work around an issue when test via xen-mceinj tools.
>>>> 
>>>> when inject simulated error via xen-mceinj tools,
>>>> status ADDRV/MISCV bits are simulated hence there is
>>>> potential risk of #GP if h/w not really support MCi_ADDR/MISC.
>>>> We temporarily work around by not clean them until we have
>>>> clean solution.
>>> 
>>> Excuse me, but - no. Changing the behavior for real MCE-s (which
>>> you added) for the benefit of fixing injection is a no-go IMO. Or
>>> are you telling us that after all that earlier change of yours is
>>> not really necessary (in which case we could as well revert it).
>>> 
>>> Jan
>>> 
>> 
>> The reason of the former patch to clear MCi_ADDR/MISC is that it's
>>              recommended by Intel SDM: LOG MCA REGISTER:
>>              SAVE IA32_MCi_STATUS;
>>              If MISCV in IA32_MCi_STATUS
>>              THEN
>>                      SAVE IA32_MCi_MISC;
>>              FI;
>>              IF ADDRV in IA32_MCi_STATUS
>>              THEN
>>                      SAVE IA32_MCi_ADDR;
>>              FI;
>>              IF CLEAR_MC_BANK = TRUE
>>              THEN
>>                      SET all 0 to IA32_MCi_STATUS;
>>              If MISCV in IA32_MCi_STATUS
>>              THEN
>>                      SET all 0 to IA32_MCi_MISC;
>>              FI;
>>              IF ADDRV in IA32_MCi_STATUS
>>              THEN
>>                      SET all 0 to IA32_MCi_ADDR;
>>              FI;
>> 
>> For Xen mce, it's meaningful to read MCi_ADDR/MISC only when real
>> error occur (which indicated by MCi_STATUS), so only clear
>> MCi_STATUS at mce handler is an acceptable work around -- after all,
>> to read MCi_ADDR/MISC is pointless if MCi_STATUS is 0.
> 
> So then what - revert your original patch (and ignore the SDM)?
> I'm not in favor of this...
> 
> Jan

Not revert entire 23327, but only use this patch to revert MCi_ADDR/MISC clear.

I also agree it's not good, but currently seems we don't have a simple and 
clean way to fix it, except we spend much time to to update xen-mceinj *tools* 
-- even so it's low-priority?

Thanks,
Jinsong
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