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

[Gonglei (Arei)]

> -----Original Message-----
> From: Kevin O'Connor [mailto:kevin at koconnor.net]
> Sent: Tuesday, December 22, 2015 2:47 AM
> To: Gonglei (Arei)
> Cc: Xulei (Stone); Paolo Bonzini; qemu-devel; seabios at seabios.org;
> Huangweidong (C); kvm at vger.kernel.org; Radim Krcmar
> Subject: Re: [Qemu-devel] [PATCH] SeaBios: Fix reset procedure reentrancy
> problem on qemu-kvm platform
> 
> On Mon, Dec 21, 2015 at 09:41:32AM +0000, Gonglei (Arei) wrote:
> > When the gurb of OS is booting, then the softirq and C function
> > send_disk_op() may use extra stack of SeaBIOS. If we inject a NMI,
> > romlayout.S: irqentry_extrastack is invoked, and the extra stack will
> > be used again. And the stack of first calling will be broken, so that the
> SeaBIOS stuck.
> >
> > You can easily reproduce the problem.
> >
> > 1. start on guest
> > 2. reset the guest
> > 3. inject a NMI when the guest show the grub surface 4. then the guest
> > stuck
> 
> Does the SeaBIOS patch below help?  

Sorry, it doesn't work. What's worse is we cannot stop SeaBIOS stuck by
Setting "CONFIG_ENTRY_EXTRASTACK=n" after applying this patch. 


> I'm not familiar with how to "inject a
> NMI" - can you describe the process in more detail?
> 

1. Qemu Command line:

#: /home/qemu/x86_64-softmmu/qemu-system-x86_64 -enable-kvm -m 4096 -smp 8 -name suse -vnc 0.0.0.0:10 \
-device virtio-scsi-pci,id=scsi0 -drive file=/home/suse11_sp3_32_2,if=none,id=drive-scsi0-0-0-0,format=raw,cache=none,aio=native \
-device scsi-hd,bus=scsi0.0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0 \
-chardev file,id=seabios,path=/home/seabios.log -device isa-debugcon,iobase=0x402,chardev=seabios \
-monitor stdio -qmp unix:/tmp/qmp,server,nowait 

2. Inject a NMI by QMP:

#: /home/qemu/scripts/qmp # ./qmp-shell /tmp/qmp
Welcome to the QMP low-level shell!
Connected to QEMU 2.5.0

(QEMU) system_reset
{"return": {}}
(QEMU) inject-nmi  
{"return": {}}
(QEMU) inject-nmi
{"return": {}}


Regards,
-Gonglei

> -Kevin
> 
> 
> --- a/src/romlayout.S
> +++ b/src/romlayout.S
> @@ -548,7 +548,9 @@ entry_post:
>          ENTRY_INTO32 _cfunc32flat_handle_post   // Normal entry point
> 
>          ORG 0xe2c3
> -        IRQ_ENTRY 02
> +        .global entry_02
> +entry_02:
> +        ENTRY handle_02  // NMI handler does not switch onto extra
> +stack
> 
>          ORG 0xe3fe
>          .global entry_13_official