Re: [Xen-devel] x2APIC MSR range (XSA-108 follow-up)

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.10.14 at 08:23, <yang.z.zhang@xxxxxxxxx> wrote:
>> The SDM 10.12.1.2 says:
>> 
>> " Addresses in the range 800HÌCBFFH that are not listed in Table 10-6
>> (including 80EH and 831H) are reserved.
>> Executions of RDMSR and WRMSR that attempt to access such addresses
>> cause general-protection exceptions. "
>> 
>> Table 10-6. Local APIC Register Address Map Supported by x2APIC
>> 
>> Why should we virtualize those reserved MSRs for guests?
> 
> IIUC the question should be why those undocumented MSRs exist on real 
> hardware and what do they do? Will guest access to them via check CPU model? 
> If yes, how can we virtualize them correctly?

Exactly. Additionally, the fact that MSRs 0xa00..0xa02 exist at least
on some CPU models already makes clear that the above cited
statement regarding raising of #GP is not really correct.

Jan

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