RE: [vMCE design RFC] Xen vMCE design

[Luck, Tony]

> 1). still use 1 bank and simply ignore this issue. I mean, even if guest 
> runs at bank0 quirks platform, when hypervisor inject vMCE# to guest, guest 
> skip bank0, then guest MCE logic would think it detect a spurious mce, then 
> kill itself. Considering bank0 quirks is only for old cpus, this is 
> acceptable;
> 2). use 32 banks
> 
> In fact, a third option is, use 1 bank, but hypervisor kill guest when it 
> detect bank0 quirks. This would be same effect as option 1, so I prefer let 
> guest kill itself.

Don't you control what CPUID is shown to the guest? Under what circumstances
would you tell the guest that it is running on an AMD-K7 or an Intel family
6 with model < 0x1A?   Surely for migration reasons you need to present the
same virtualized family/model all the time ... so just don't use ones that
cause problems.

If that isn't an option - then say there are 2 banks and have Xen ignore bank
0 (make MC0_STATUS always appear to contain 0) and put all the errors into
bank1.  If you tell the guest there are 32 banks it will read all of them.
Which means a lot of pointless exits to the hypervisor.

-Tony
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