On 10/08/2012 04:01:11 PM, Alexander Graf wrote:
On 08.10.2012, at 22:45, Scott Wood wrote:
> On 10/07/2012 08:30:06 AM, Alexander Graf wrote:
>> On 07.10.2012, at 15:26, Avi Kivity wrote:
>> > The downside of this generic approach is that it prepares
suprises down
>> > the road. The alternative approach, of adding a new
KVM_EXIT_RESET,
>> > avoids this minefield, but requires ABI changes every time we
want to
>> > emulate something in userspace. Can you provide a critique of
this
>> > alternate approach?
>> Yeah, it doesn't scale as well. The SPR read/write give us all
information we need to emulate other registers too, like the magical
"read this SPR and automatically get the interrupt vector from the
MPIC and ack the interrupt along the way" register we have on e500.
>
> That's not actually how the register works in hardware (though it
may be a reasonable way to emulate it with a userspace mpic). The
interrupt is acknowledged when the core branches to the interrupt
vector. The register itself is just storage that gets filled when
that happens.
Mind to enlighten me again on how exactly this mode gets enabled so
that an OS that does not make use of the SPR can still ask the MPIC
by hand :)?
GCR[M] is set to 3 for external proxy mode, versus 1 for traditional
operation.
-Scott
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