On 23.07.2018 22:16, Collin Walling wrote:
On 07/21/2018 12:05 AM, Chris Venteicher wrote:
Quoting David Hildenbrand (2018-07-18 02:26:24)
On 18.07.2018 00:39, Collin Walling wrote:
On 07/17/2018 05:01 PM, David Hildenbrand wrote:
On 13.07.2018 18:00, Jiri Denemark wrote:
On Mon, Jul 09, 2018 at 22:56:55 -0500, Chris Venteicher wrote: > Transient S390 configurations require using QEMU to compute CPU Model > Baseline and to do CPU Feature Expansion. > > Start and use a single QEMU instance to do both the baseline and > expansion transactions required by BaselineHypervisorCPU. > > CPU Feature Expansion uses true / false to indicate if property is/isn't > included in model. Baseline only returns property list where all > enumerated properties are included.
So are you saying on s390 there's no chance there would be a CPU model with some feature which is included in the CPU model disabled for some reason? Sounds too good to be true :-) (This is the question I referred to in one of my replies to the other patches.)
Giving some background information: When we expand/baseline CPU models, we always expand them to the "-base" variants of our CPU models, which contain some set of features we expect to be around in all sane configurations ("minimal feature set").
It is very unlikely that we ever have something like "z14-base,featx=off", but it could happen - When using an emulator (TCG) - When running nested and the guest hypervisor is started with such a strange CPU model - When something in the HW is very wrong or eventually removed in the future (unlikely but possible)
On some very weird inputs to a baseline request, such a strange model can also be the result. But it is very unusual.
I assume something like "baseline z14-base,featx=off with z14-base" will result in "z14-base,featx=off", too.
That's correct. A CPU model with a feature disabled that is baseline with a CPU model with that same feature enabled will omit that feature in the QMP response.
e.g. if z14-base has features x, y, z then
"baseline z14-base,featx=off with z14-base" will result in "z14-base,featy=on,featz=on"
I am runing tests on both S390 and X86 (hacked QEMU to enable baseline).
I don't see a "false" property in the baseline response in any of the logs.
Right... baseline should not be returning any properties paired with false. It constructs a third CPU model with properties that can run on both CPUs.
Let me rephrase: We don't return "false" for any property when baselining as of now, but this might change in the future. It is undocumented behavior. -- Thanks, David / dhildenb