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Date: Mon, 04 Mar 2013 13:21:10 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v13 0/8] pv event interface between host
	and guest
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To: Gleb Natapov <gleb@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, kvm list <kvm@vger.kernel.org>, "Michael S. Tsirkin" <mst@redhat.com>, Hu Tao <hutao@cn.fujitsu.com>, 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>, Jan Kiszka <jan.kiszka@siemens.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>, Kevin Wolf <kwolf@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Marcelo Tosatti <mtosatti@redhat.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>

Il 04/03/2013 12:52, Gleb Natapov ha scritto:
> > Same here, you can remove the panic event port and add debugcon at
> > 0x505.  That's the problematic case.  But if the user goes to that
> > length, I think we can honestly say we don't care.
>
> IMO there is a big difference between well know serial ISA ports and
> PIO ports we allocate for our devices. Later have to be discoverable
> without resorting to probing. On CPU level we do the same with CPUID
> bits instead of relaying on MSRs #GP. On KVM API level we do the same
> with capabilities instead of relying on ioctls returning errors. This
> is not different.

Ok, I see your point now.  Yes, this is a good reason why patching is
better in the long run.

Paolo