From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54852) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e7dLt-0000wK-3i for qemu-devel@nongnu.org; Thu, 26 Oct 2017 04:17:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e7dLp-0007oo-TB for qemu-devel@nongnu.org; Thu, 26 Oct 2017 04:17:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54382) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e7dLp-0007nX-M3 for qemu-devel@nongnu.org; Thu, 26 Oct 2017 04:17:17 -0400 Date: Thu, 26 Oct 2017 10:17:09 +0200 From: Cornelia Huck Message-ID: <20171026101709.7c7b47ff.cohuck@redhat.com> In-Reply-To: <20171020145437.18549-1-borntraeger@de.ibm.com> References: <20171020145437.18549-1-borntraeger@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH/QEMU] s390x/kvm: use cpu_model_available for guarded storage on compat machines List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christian Borntraeger Cc: Marc Hartmayer , libvir-list@redhat.com, qemu-devel@nongnu.org, Jiri Denemark , Boris Fiuczynski , "Jason J . Herne" , Viktor Mihajlovski On Fri, 20 Oct 2017 16:54:37 +0200 Christian Borntraeger wrote: > Starting a guest with > > hvm > > > > on an IBM z14 results in > > "qemu-system-s390x: Some features requested in the CPU model are not > available in the configuration: gs" > > This is because guarded storage is fenced for compat machines that did not have > guarded storage support, but libvirt expands the cpu model according to the > latest available machine. > > While this prevents future migration abort (by not starting the guest at all), > not being able to start a "host-model" guest is very much unexpected. As it > turns out, even if we would modify libvirt to not expand the cpu model to > contain "gs" for compat machines, it cannot guarantee that a migration will > succeed. For example if the kernel changes its features (or the user has > nested=1 on one host but not on the other) the migration will fail > nevertheless. So instead of fencing "gs" for machines <= 2.9 lets allow it for > all machine types that support the CPU model. This will make "host-model" > runnable all the time, while relying on the CPU model to reject invalid > migration attempts. > > Suggested-by: David Hildenbrand > Signed-off-by: Christian Borntraeger > --- > hw/s390x/s390-virtio-ccw.c | 8 -------- > include/hw/s390x/s390-virtio-ccw.h | 3 --- > target/s390x/kvm.c | 2 +- > 3 files changed, 1 insertion(+), 12 deletions(-) Acked-by: Cornelia Huck