From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49512) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dxA4D-0003Yb-Vq for qemu-devel@nongnu.org; Wed, 27 Sep 2017 06:59:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dxA4A-0003Cv-0m for qemu-devel@nongnu.org; Wed, 27 Sep 2017 06:59:50 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:50076) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dxA49-0003Az-Nw for qemu-devel@nongnu.org; Wed, 27 Sep 2017 06:59:45 -0400 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v8RAwtYP045361 for ; Wed, 27 Sep 2017 06:59:40 -0400 Received: from e06smtp14.uk.ibm.com (e06smtp14.uk.ibm.com [195.75.94.110]) by mx0a-001b2d01.pphosted.com with ESMTP id 2d83qrn1hm-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 27 Sep 2017 06:59:40 -0400 Received: from localhost by e06smtp14.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 27 Sep 2017 11:59:38 +0100 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> From: Christian Borntraeger Date: Wed, 27 Sep 2017 12:59:35 +0200 MIME-Version: 1.0 In-Reply-To: <20170927125606.65dc514d.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Message-Id: <14df9ad6-f0e9-cd51-04dd-4fe994808433@de.ibm.com> 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: Cornelia Huck , Yi Min Zhao Cc: David Hildenbrand , qemu-devel@nongnu.org, agraf@suse.de, pasic@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com, dgilbert@redhat.com On 09/27/2017 12:56 PM, Cornelia Huck wrote: > On Wed, 27 Sep 2017 18:25:00 +0800 > Yi Min Zhao wrote: >=20 >> =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: >=20 >>>> I'd really really really (did I mention really?) favor something lik= e a >>>> dummy device, because we could easily handle the !CONFIG_PCI case th= en. >>>> >>>> All these compat options and conditions will kill us someday... we'r= e >>>> already patching around that whole stuff way too much. >>>> >>>> If we ever unconditionally created a device, we should keep doing so= . =20 >>> Yes, that whole thing is horrible, especially interaction with compat >>> 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. >=20 > 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... For this particular case your initial patch might be less problematic tha= n a dummy device, because the code that does the migration is NOT contained in s390 specific code but in common PCI code instead. We would need to ke= ep the dummy device always in a way that it will work with the common PCI code.