From: Kevin O'Connor [mailto:kevin@koconnor.net] Sent: Saturday, December 19, 2015 7:13 AM To: Gonglei (Arei) Cc: Xulei (Stone); Paolo Bonzini; qemu-devel; seabios@seabios.org; Huangweidong (C); kvm@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