On 05/03/2013 03:56:47 PM, Caraman Mihai Claudiu-B02008 wrote:
> -----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@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx;
> linuxppc-dev@xxxxxxxxxxxxxxxx
> 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,
Hmm... I don't see any obvious breakage from that, but it makes me
nervous. I'd be more comfortable if we just hard-disabled interrupts
there.
when do we hard-disable interrupts?
Interrupts will be hard-disabled when we take an exception to exit
guest state.
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.
I replaced the two calls to kvmppc_lazy_ee_enable() with calls to
hard_irq_disable(), and it seems to be working fine.
> > > 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}
Sigh. I meant the real caller, who's calling local_irq_restore().
-Scott
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