[PATCH 10/13] kvm/powerpc: Add support for Book3S processors in hypervisor mode

[Paul Mackerras]

On Tue, May 17, 2011 at 12:17:50PM +0200, Alexander Graf wrote:
> 
> On 16.05.2011, at 07:58, Paul Mackerras wrote:
> 
> > I do the check there because I was having problems where, if the HDEC
> > goes negative before we do the partition switch, we would occasionally
> > not get the HDEC interrupt at all until the next time HDEC went
> > negative, ~ 8.4 seconds later.
> 
> Yikes - so HDEC is edge and doesn't even keep the interrupt line up?
> That sounds like a serious hardware limitation. What if you only use
> HDEC and it triggers while interrupts are off in a critical section?
> Is the hardware really that broken?

If HDEC expires when interrupts are off, the HDEC interrupt stays
pending until interrupts get re-enabled.  I'm not sure exactly what
the conditions are that cause an HDEC interrupt to get lost, but they
seem to involve at least a partition switch.

Paul.