On 06.06.2017 10:39, Christian Borntraeger wrote: > On 06/02/2017 07:28 PM, Halil Pasic wrote: > [...] >> Maybe integrating some of the discussion from above into the commit >> message would be helpful. > > applied with the following patch description
Just wanted to ask you to do that :) Thanks! Looks good to me! > > > Currently, under z/VM on a 0x2827, QEMU will detect a 0x2828 if no > IBC value is provided. QEMU will simply take the last model of that HW > generation, which happens to be the BC version. > > Let's improve our search for that case by selecting the latest CPU > definition that matches the CPU type. This for example will avoid > detecting an z13 as a z13s. > > We might still detect a GA2 version on a GA1 system, but as we don't > have further information at hand, there isn't too much we can do about > it. The alternative of always presenting the oldest GA is not backward > compatible, e.g: > You're running on 0x2827 GA2. > Old QEMU version indicated "0x2828 GA1 == 0x2827 GA2". After you updated > QEMU, you suddenly detect "0x2827 GA1". You're previous libvirt guest > might suddenly refuse to run. > > In the end presenting a newer GA level does not matter because: > > 1: All GAX models share the same base feature set. A GAX++ might > support "more features". > 2: Without an IBC, the guest can't detect the GA version. > > If we have no IBC (esp. unblocked_ibc == 0), the IBC we will present > to the guest in read_SCP_info() will be 0. The guest will not know > which GA version it has. The problem of missing IBC propagates. > > If we don't have a feature of the GA++ version, also our guest won't > have it. So in summary, the guest also has no idea of its GA version. > > Signed-off-by: David Hildenbrand <da...@redhat.com> > Message-Id: <20170531193434.6918-3-da...@redhat.com> > Acked-by: Jason J. Herne <jjhe...@linux.vnet.ibm.com> > Reviewed-by: Halil Pasic <pa...@linux.vnet.ibm.com> > Signed-off-by: Christian Borntraeger <borntrae...@de.ibm.com> > [improve patch description by reusing mailing list discussion] > > -- Thanks, David
