Re: [Xen-devel] [PATCH 2/2] x86/vMCE: save/restore MCA capabilities

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.03.12 at 10:28, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
> Jan Beulich wrote:
>> But we're getting all the farther away from the actual question: Do
>> we need to provide for saving/restoring of any of the _CTL
>> registers?
>> 
> 
> Per Tony's elaboration about _CTL h/w meaning, I thought they are model 
> specific mainly used for debug purpose and os defaultly set all 1's to them 
> (if any misunderstanding please point out to me).
> So how about unbind _CTL with host (say, pure software emulated msr, not 
> involve h_mcg_ctl/h_mci_ctrl[bank])? If so we don't need save/restore _CTL. 
> After all they are model specific, and emulated as all 1's to guest seems 
> reasonable.

If the guest OS considers a particular CPU model to require an
adjustment to any of these, any such adjustment would be lost over
migration. I'm simply uncertain whether all OSes will tolerate that (in
which case ignoring the writes in the first place would probably be
better).

Jan


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