From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40494) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dxBLf-0002eR-5I for qemu-devel@nongnu.org; Wed, 27 Sep 2017 08:21:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dxBLZ-0003v6-8x for qemu-devel@nongnu.org; Wed, 27 Sep 2017 08:21:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41098) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dxBLZ-0003uj-2g for qemu-devel@nongnu.org; Wed, 27 Sep 2017 08:21:49 -0400 References: <20170926162058.30772-1-cohuck@redhat.com> <20170926162058.30772-2-cohuck@redhat.com> <338c8565-691e-a8bc-d8a6-3637ce13701d@redhat.com> <20170927114717.72bd69f8.cohuck@redhat.com> <20170927125606.65dc514d.cohuck@redhat.com> <14df9ad6-f0e9-cd51-04dd-4fe994808433@de.ibm.com> From: David Hildenbrand Message-ID: <4681e677-9e5a-4c1c-8e22-dc5c51b7286d@redhat.com> Date: Wed, 27 Sep 2017 14:21:45 +0200 MIME-Version: 1.0 In-Reply-To: <14df9ad6-f0e9-cd51-04dd-4fe994808433@de.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH 1/1] s390x: create a compat s390 phb for <=2.10 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christian Borntraeger , Cornelia Huck , Yi Min Zhao Cc: qemu-devel@nongnu.org, agraf@suse.de, pasic@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com, dgilbert@redhat.com On 27.09.2017 12:59, Christian Borntraeger wrote: >=20 >=20 > On 09/27/2017 12:56 PM, Cornelia Huck wrote: >> On Wed, 27 Sep 2017 18:25:00 +0800 >> Yi Min Zhao wrote: >> >>> =E5=9C=A8 2017/9/27 =E4=B8=8B=E5=8D=885:47, Cornelia Huck =E5=86=99=E9= =81=93: >>>> On Tue, 26 Sep 2017 20:40:25 +0200 >>>> David Hildenbrand wrote: >> >>>>> I'd really really really (did I mention really?) favor something li= ke a >>>>> dummy device, because we could easily handle the !CONFIG_PCI case t= hen. >>>>> >>>>> All these compat options and conditions will kill us someday... we'= re >>>>> already patching around that whole stuff way too much. >>>>> >>>>> If we ever unconditionally created a device, we should keep doing s= o. =20 >>>> Yes, that whole thing is horrible, especially interaction with compa= t >>>> machines. >>>> >>>> Do you have an idea on how to create such a dummy device (without >>>> having to effectively copy a lot of configured-out code)? >>>> >>>> =20 >>> How about in s390_pcihost_hot_plug() we check s390_has_feat(zpci)? >>> If no zpci feature, we avoid plugging any pci device. >>> Then we could always create phb. >>> I think pcibus's vmstate is only data to migrate. >> >> That's still problematic if CONFIG_PCI is off. I currently don't have = a >> better idea than either disallowing compat machines on builds without >> pci, or using a dummy device... >=20 > For this particular case your initial patch might be less problematic t= han > a dummy device, because the code that does the migration is NOT contain= ed > in s390 specific code but in common PCI code instead. We would need to = keep > the dummy device always in a way that it will work with the common PCI > code. >=20 Interesting, so how is migration then handled for e.g. x86 or other architectures that can work without CONFIG_PCI? I assume their migration should also break? --=20 Thanks, David