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Date: Sat, 30 Mar 2013 16:36:48 +0100
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Subject: Re: [Qemu-devel] [SeaBIOS] [PATCH v16] Add pvpanic device driver
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To: Kevin O'Connor <kevin@koconnor.net>
Cc: Marcelo Tosatti <mtosatti@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, Andrew Jones <drjones@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Alex Williamson <alex.williamson@redhat.com>, Juan Quintela <quintela@redhat.com>, Gleb Natapov <gleb@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Hu Tao <hutao@cn.fujitsu.com>, seabios@seabios.org, qemu-devel <qemu-devel@nongnu.org>, Markus Armbruster <armbru@redhat.com>, Blue Swirl <blauwirbel@gmail.com>, Orit Wasserman <owasserm@redhat.com>, Alexander Graf <agraf@suse.de>, Sasha Levin <levinsasha928@gmail.com>, Stefan Hajnoczi <stefanha@redhat.com>, Jan Kiszka <jan.kiszka@siemens.com>, Luiz Capitulino <lcapitulino@redhat.com>, Christian Borntraeger <borntraeger@de.ibm.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Il 30/03/2013 14:20, Kevin O'Connor ha scritto:
> On Fri, Mar 29, 2013 at 02:49:12PM +0100, Paolo Bonzini wrote:
>> Il 29/03/2013 14:33, Kevin O'Connor ha scritto:
>>> On Fri, Mar 29, 2013 at 04:18:44PM +0800, Hu Tao wrote:
>>>> pvpanic device is used to notify host(qemu) when guest panic happens.
>>>
>>> Thanks.  However, we're planning a move of ACPI tables from SeaBIOS to
>>> QEMU.  I think this should wait until after the move.
>>
>> The device should be in QEMU 1.5, and the SSDT probably will still be in
>> SeaBIOS by then (and might even be the last to move, since it's quite
>> complex and dynamic).  I don't think it is fair to block this patch on
>> those grounds...
> 
> What is the user visible impact of not having a panic device?

Management cannot restart or dump the guest after a panic, and cannot
log that a panic happened (as opposed to a random watchdog event).

> My main concern is that the patch creates a new fw_cfg channel between
> qemu and seabios thats sole purpose is to alter the OS visible ACPI
> tables.  These types of QEMU->SeaBIOS interfaces are fragile and are
> (in sum) quite complex.

Yes, this is true.

Paolo