RE: [Xen-devel] [PATCH] DOM0: Adding MCA Loging support in DOM0

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> "Ke, Liping" <liping.ke@xxxxxxxxx> 01.07.09 03:42 >>>
>Jan Beulich wrote:
>> Actually, there are still two issues with this:
>> 
>> First, shouldn't bind_virq_for_mce() and the associated message
>> printing 
>> really only happen on Dom0 (i.e. be guarded by
>> is_initial_xendomain()), 
>> just like the name suggests?
>
>Yes. DOM0 is the only one who's responsible for MCE logging (Even 
>the error address belongs to other Guest). Currently mce_dom0.o is 
>only compiled when it is a privileged guest [depends on 
>(!XEN_UNPRIVILEGED_GUEST)
>according to Kconfig]. bind_virq_for_mce() is also protected by the same thing
> [#if defined(CONFIG_X86_XEN_MCE)] You mean we still need other guard?

!XEN_UNPRIVILEGED_GUEST doesn't mean the kernel can't run as DomU,
it's only the other way around. Hence a build-time check only isn't sufficient.

>> 
>> Second, I'm now seeing
>> 
>> (XEN) traps.c:2263:d0 Domain attempted WRMSR 000000000000017b from
>> 00000000:0000003f to ffffffff:ffffffff. (XEN) traps.c:2263:d0 Domain
>> attempted WRMSR 0000000000000400 from 00000000:000000ff to
>> ffffffff:ffffffff. (XEN) traps.c:2263:d0 Domain attempted WRMSR
>> 0000000000000404 from 00000000:ffffffff to ffffffff:ffffffff. (XEN)
>> traps.c:2263:d0 Domain attempted WRMSR 0000000000000408 from
>> 00000000:00000fff to ffffffff:ffffffff. (XEN) traps.c:2263:d0 Domain
>> attempted WRMSR 000000000000040c from 00000000:00000003 to
>> ffffffff:ffffffff. (XEN) traps.c:2263:d0 Domain attempted WRMSR
>> 0000000000000410 from 00000000:3fffffff to ffffffff:ffffffff. (XEN)
>> traps.c:2263:d0 Domain attempted WRMSR 0000000000000414 from
>> 00000000:00000001 to ffffffff:ffffffff.     
>> 
>> which isn't really nice.
>
>I looked into the code, current CONFIG_X86_MCE is defaultly 'y', so mce.o 
>DOM0 will be compiled by default. Yet we now only support intel 64 bit for 
>DOM0 vMSR. I guess this is the reason why you see those printings. 
>Shall I sent a patch to make stricker limitations for compiling mce.o? 

I'm not sure if you can avoid compiling mce.o altogether - if that's possible,
it would certainly be the best approach. If not, some other mechanism to
suppress the actual hardware touching bits would be desirable.

Jan


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