Re: nmi is broken?

[Avi Kivity <avi@redhat.com>]

On 05/03/2011 04:25 PM, OGAWA Hirofumi wrote:
> Avi Kivity<avi@redhat.com>  writes:
>
> >  On 05/03/2011 12:36 PM, Avi Kivity wrote:
> >>
> >>>  I don't know about live migration of kvm. If we said the wiring is like
> >>>  figure 5-2, what is required for the live migration? It was required
> >>>  only if IMCR was required?
> >>
> >>  The issue with live migration is that we can't change the running
> >>  configuration while the system is running, like adding the IMCR or
> >>  changing the wiring.  The hardware will be programmed for the old
> >>  configuration and will likely fail with the new one.  For example, the
> >>  current wiring has the PIT output wired to PIC IRQ0 and IOAPIC INTI0;
> >>  we need to change it to IOAPIC INTI2 instead.
> >>
> >
> >  btw, I believe that the configuration currently implemented is legal
> >  (it's similar to config 7 in table 5-2 of the mpspec); the only problem
> >  is that it can't support the NMI watchdog through the I/O APIC trick,
> >  yet we allow it through a hack.
>
> I'm confused a bit. "config 7 in table 5-2" says PIT output wired to
> IOAPIC INTIN2. So, we don't need to change it?

We're like config 7 in that the 8259A output isn't wired to the IOAPIC.  
However we're unlike config 7 in that the PIT output is wired to IOAPIC 
INTIN0.  I think we can keep it that way.

> >  Something we can do is connect the 8259A output to the I/O APIC INTIN2;
> >  it should be masked so live migration will continue to work.  We just
> >  have to make sure that the guest is able to find that it is connected there.
>
> 8259A INTR to IOAPIC INTIN2 sounds strange. Isn't it IOAPIC INTIN0?

Usually yes, but we already have the PIT wired to INTIN0.  I saw that 
the kernel consults the mptable to see which pin to use, so with the 
right BIOS magic we can get things to work.

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