On 31.01.2013, at 19:54, Scott Wood wrote:

> On 01/31/2013 12:52:41 PM, Alexander Graf wrote:
>> On 31.01.2013, at 19:43, Scott Wood wrote:
>> > On 01/31/2013 12:21:07 PM, Alexander Graf wrote:
>> >> How about something like this? Then both targets at least suck as much :).
>> >
>> > I'm not sure that should be the goal...
>> >
>> >> Thanks to e500mc's awful hardware design, we don't know who sets the 
>> >> MSR_DE bit. Once we forced it onto the guest, we have no change to know 
>> >> whether the guest also set it or not. We could only guess.
>> >
>> > MSRP[DEP] can prevent the guest from modifying MSR[DE] -- but we still 
>> > need to set it in the first place.
>> >
>> > According to ISA V2.06B, the hypervisor should set DBCR0[EDM] to let the 
>> > guest know that the debug resources are not available, and that "the value 
>> > of MSR[DE] is not specified and not modifiable".
>> So what would the guest do then to tell the hypervisor that it actually 
>> wants to know about debug events?
> 
> The guest is out of luck, just as if a JTAG were in use.

Hrm.

Can we somehow generalize this "out of luck" behavior?

Every time we would set or clear an MSR bit in shadow_msr on e500v2, we would 
instead set or clear it in the real MSR. That way only e500mc is out of luck, 
but the code would still be shared.


Alex

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