Re: [Xen-devel] Xen mce bugfix

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.02.13 at 12:08, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
> Jan Beulich wrote:
>>>>> On 27.02.13 at 11:37, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
>>> 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...
> 
> 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?

No, fixing the tool seems unnecessary for this problem, all we
need is a way to avoid the problematic MSR writes when finishing
an injected MCE. That's fully contained to the hypervisor.

Jan


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