[Skiboot] [PATCH 1/6] Enable attn instruction on boot

Patrick Williams patrick at stwcx.xyz
Sat Apr 30 04:59:59 AEST 2016

On Fri, Apr 29, 2016 at 03:57:02PM +1000, Michael Neuling wrote:
> Currently we leave the attn instruction disabled until we use.  This
> means that attn is not available to the host kernel.
> This enables the attn instruction on all CPUs on boot.
> Signed-off-by: Michael Neuling <mikey at neuling.org>

Are you sure this is a good idea?  I was under the impression that once
the attn instruction is enabled any privilege level could execute it
and it would actually cause an attn.  Are you certain that only
hypervisor level code is able to execute attn and cause the effect?  You
don't want to have virtual machines executing attn and bringing down
your system.

I can't find the instruction documented in the ISA (2.07 or 3.0) to know
for certain.
Patrick Williams
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