[PATCH] KVM: PPC: Book3E 64: Fix IRQs warnings and hangs

[Caraman Mihai Claudiu-B02008]

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Friday, May 03, 2013 11:15 PM
> To: Caraman Mihai Claudiu-B02008
> Cc: Wood Scott-B07421; kvm-ppc at vger.kernel.org; kvm at vger.kernel.org;
> linuxppc-dev at lists.ozlabs.org
> Subject: Re: [PATCH] KVM: PPC: Book3E 64: Fix IRQs warnings and hangs
> 
> > > > The unresponsiveness has to do with the fact that
> > > > arch_local_irq_restore()
> > > > does not guarantees to hard enable interrupts.
> > >
> > > Could you elaborate?  If the saved IRQ state was "enabled", why
> > > wouldn't arch_local_irq_restore() hard-enable IRQs?  The last thing
> > it
> > > does is __hard_irq_enable().
> >
> > 	if (!irq_happened)
> > 		return;
> 
> OK, so the problem is that we're not setting PACA_IRQ_HARD_DIS when we
> hard-disable interrupts?

We enter guest with local_irq_disable() which means soft disabled, when
do we hard-disable interrupts? If we follow host exception handlers model
they set PACA_IRQ_EE/DEC/DBELL but not PACA_IRQ_HARD_DIS. Can you give it
a try to see how KVM behaves with PACA_IRQ_HARD_DIS? I can't do it right now.

> 
> > > Where is the arch_local_irq_restore() instance you're talking about?
> >
> > ./arch/power/kernel/irq.c
> 
> I meant the caller. :-P

./arch/powerpc/include/asm/hw_irq.h

  55static inline unsigned long arch_local_irq_disable(void)
  56{
  57        unsigned long flags, zero;
  58
  59        asm volatile(
  60                "li %1,0; lbz %0,%2(13); stb %1,%2(13)"
  61                : "=r" (flags), "=&r" (zero)
  62                : "i" (offsetof(struct paca_struct, soft_enabled))
  63                : "memory");
  64
  65        return flags;
  66}
  67
  68extern void arch_local_irq_restore(unsigned long);
  69
  70static inline void arch_local_irq_enable(void)
  71{
  72        arch_local_irq_restore(1);
  73}

-Mike