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

[Kevin O'Connor]

On Fri, Dec 18, 2015 at 03:04:58AM +0000, Gonglei (Arei) wrote:
> Hi Kevin & Paolo,
> 
> Luckily, I reproduced this problem last night. And I got the below log when 
> SeaBIOS is stuck.
[...]
> [2015-12-18 10:38:10]  gonglei: finish while   
[...]
> <...>-31509 [035] 154753.180077: kvm_exit: reason EXCEPTION_NMI rip 0x3 info 
> 0 80000306
> <...>-31509 [035] 154753.180077: kvm_emulate_insn: 0:3:f0 53 (real)
> <...>-31509 [035] 154753.180077: kvm_inj_exception: #UD (0x0)
> <...>-31509 [035] 154753.180077: kvm_entry: vcpu 0

This is an odd finding.  It seems to indicate that the code is caught
in an infinite irq loop once irqs are enabled.  What doesn't make
sense is that an NMI shouldn't depend on the cpu irq enable flag.
Also, I can't explain why rip would be 0x03, nor why a #UD in an
exception handler wouldn't result in a triple fault.  Maybe someone
with more kvm knowledge could help here.

I did notice that you appear to be running with SeaBIOS v1.8.1 - I
recommend you upgrade to the latest.  There were two important fixes
in this area (8b9942fa and 3156b71a).  I don't think either of these
fixes would explain the log above, but it would be best to eliminate
the possibility.

-Kevin