From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50201) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UtoMF-00023x-Fl for qemu-devel@nongnu.org; Mon, 01 Jul 2013 20:22:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UtoME-0002Go-3O for qemu-devel@nongnu.org; Mon, 01 Jul 2013 20:22:11 -0400 Mime-Version: 1.0 (Apple Message framework v1278) Content-Type: text/plain; charset=us-ascii From: Alexander Graf In-Reply-To: <20130702000635.GA4729@voom.fritz.box> Date: Tue, 2 Jul 2013 02:21:59 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <6A17A370-6FC7-4912-8B9E-9E51280F3BAB@suse.de> References: <1372315560-5478-1-git-send-email-aik@ozlabs.ru> <1372315560-5478-3-git-send-email-aik@ozlabs.ru> <20130627114719.GG10614@voom.fritz.box> <51CC2D4F.9000401@ozlabs.ru> <20130702000635.GA4729@voom.fritz.box> Subject: Re: [Qemu-devel] [PATCH 02/17] pseries: rework XICS List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: Anthony Liguori , Alexey Kardashevskiy , qemu-devel@nongnu.org, qemu-ppc@nongnu.org, Paolo Bonzini , Paul Mackerras On 02.07.2013, at 02:06, David Gibson wrote: > On Thu, Jun 27, 2013 at 10:17:19PM +1000, Alexey Kardashevskiy wrote: >> On 06/27/2013 09:47 PM, David Gibson wrote: >>> On Thu, Jun 27, 2013 at 04:45:45PM +1000, Alexey Kardashevskiy = wrote: >>>> Currently XICS interrupt controller is not a QEMU device. As we are = going >>>> to support in-kernel emulated XICS which is a part of KVM, it make >>>> sense not to extend the existing XICS and have multiple KVM stub = functions >>>> but to create yet another device and share pieces between fully = emulated >>>> XICS and in-kernel XICS. >>>=20 >>> Hmm. So, I think changing the xics to the qdev/qom framework is a >>> generally good idea. But I'm not convinced its a good idea to have >>> different devices for the kernel and non-kernel xics. >>=20 >> The idea came from Alex Graf, this is already done for = openpic/openpic-kvm. >> The normal practice is to move ioctls to KVM to KVM code and provide = empty >> stubs for non-KVM case. There were too many so having a separate = xics-kvm >> is kind of help. >>=20 >>=20 >>> Won't that >>> prevent migrating from a system with a kernel xics to one without, = or >>> vice versa? >>=20 >> Mmm. Do we care much about that?... >=20 > Enough to avoid making it impossible by design. We went that route with x86 too after lots of hassle trying to shoehorn = the in-kernel APIC into the emulation device. It's more hassle than = gain. >=20 >> At the moment it is not supported that as VMStateDescription have = different >> .name for xics and xics-kvm but easy to fix. And we do not pass a = device to >> vmstate_register so that must be it. >=20 > Ok, if you can make the ids in the vmsd match, then that should be ok. I really just wouldn't bother too much about it. Sooner or later = QEMU-XICS is going to be a legacy and debug only option. Alex