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Date: Sun, 31 Mar 2013 17:34:10 +0300
From: Gleb Natapov <gleb@redhat.com>
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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: Peter Maydell <peter.maydell@linaro.org>, "Michael S. Tsirkin" <mst@redhat.com>, Jan Kiszka <jan.kiszka@siemens.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>, Juan Quintela <quintela@redhat.com>, Alexander Graf <agraf@suse.de>, Christian Borntraeger <borntraeger@de.ibm.com>, Hu Tao <hutao@cn.fujitsu.com>, Andrew Jones <drjones@redhat.com>, Alex Williamson <alex.williamson@redhat.com>, Sasha Levin <levinsasha928@gmail.com>, Stefan Hajnoczi <stefanha@redhat.com>, Luiz Capitulino <lcapitulino@redhat.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Anthony Liguori <aliguori@us.ibm.com>, Marcelo Tosatti <mtosatti@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>

On Sat, Mar 30, 2013 at 09:20:09AM -0400, Kevin O'Connor wrote:
> 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?
> 
> 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.
> 
The patch uses existing channel between qemu and seabios, one
romfile_loadint() is all it takes. We already have number of interfaces
to change OS visible ACPI tables, that's why we want to move ACPI table
creation to QEMU in the first place. It is unfortunate to start blocking
features now before we have an alternative. When ACPI table creation
will move into QEMU the code in this patch will be dropped along with
all the other code that serves similar purpose.

--
			Gleb.