Re: [Qemu-devel] [PATCH] SeaBios: Fix reset procedure reentrancy problem on qemu-kvm platform

[Kevin O'Connor]

On Sat, Dec 19, 2015 at 12:03:15PM +0000, Gonglei (Arei) wrote:
> Maybe the root cause is not NMI but INTR, so yield() can open hardware 
> interrupt,
> And then execute interrupt handler, but the interrupt handler make the SeaBIOS
> stack broken, so that the BSP can't execute the instruction and occur 
> exception,
> VM_EXIT to Kmod, which is an infinite loop. But I don't have any proofs except
> the surface phenomenon.

I can't see any reason why allowing interrupts at this location would
be a problem.

> Kevin, can we drop yield() in smp_setup() ?

It's possible to eliminate this instance of yield, but I think it
would just push the crash to the next time interrupts are enabled.

> Is it really useful and allowable for SeaBIOS? Maybe for other components?
> I'm not sure. Because we found that when SeaBIOS is booting, if we inject a
> NMI by QMP, the guest will *stuck*. And the kvm tracing log is the same with
> the current problem.

If you apply the patches you had to prevent that NMI crash problem,
does it also prevent the above crash?

-Kevin