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

[Gonglei (Arei)]

>
> From: Kevin O'Connor [mailto:kevin at koconnor.net]
> Sent: Saturday, December 19, 2015 7:13 AM
> To: Gonglei (Arei)
> Cc: Xulei (Stone); Paolo Bonzini; qemu-devel; seabios at seabios.org;
> Huangweidong (C); kvm at vger.kernel.org
> Subject: Re: [Qemu-devel] [PATCH] SeaBios: Fix reset procedure reentrancy
> problem on qemu-kvm platform
> 
> 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.
> 

Ccing Paolo and Radim.

> 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.
> 
We can reproduce the problem using latest SeaBIOS too. :(


Regards,
-Gonglei