Re: [Xen-devel] [xen vMCE RFC V0.2] xen vMCE design

[Christoph Egger]

On 07/03/12 15:26, Luck, Tony wrote:

>> I'm not convinced of the need, and would prefer aiming at a
>> shared implementation unless issues arise that make this
>> impossible.
> 
> It does sound odd. Yes, Intel and AMD have differences around CMCI ... but we are never
> going to send a CMCI to a guest (there is no point, it can't do anything useful with the
> information, it may do something pointlessly stupid like stop using a guest physical page).
> The only reason I suggested making MCG_CAP pretend that CMCI was supported was a
> small optimization ... if a Linux guest sees that CMCI is supported, it will not poll the machine
> check banks looking for corrected errors.


Are you talking about PV or HVM guest?

For HVM guests yes it makes sense to disable CMCI in MCG_CAP for both
AMD and Intel.

PV guests never read MCE MSRs directly. They install a trap handler and
use the hypercall to fetch the error telemetry. The xen interface is
common to both AMD and Intel - it's basically just an array of bytes.
The first bytes tell you how you can cast and interpret the bytes.
That *content* is specific to AMD or Intel.

How much logic can be shared is almost a matter of software design
and not hardware design.

Christoph

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