On Mon, 11 Feb 2019 09:55:25 +0100
David Hildenbrand <da...@redhat.com> wrote:
> On 11.02.19 09:28, Christian Borntraeger wrote:
> >
> >
> > On 11.02.2019 09:23, Cornelia Huck wrote:
> >> On Fri, 8 Feb 2019 17:11:10 -0500
> >> Collin Walling <wall...@linux.ibm.com> wrote:
> >>
> >>> Latest systems and host kernels support mepoch, which is a
> >>> feature that was meant to be supported for z14 GA1 from the
> >>> get-go. Let's copy it to the z14 GA1 default CPU model.
> >>
> >> Do older kernels simply not support it, or was there something actively
> >> missing? IOW, is it fine to turn this on with older kernels?
> >
> > Older kernels will not provide the necessary implementation, so mepoch will
> > not
> > work with such older kernel. (So worst case would be that a new qemu+old
> > kernel
> > requires to add mepoch=off to -cpu z14)
>
> Or use a compat machine.
>
> > The idea of this patch is to update QEMU in accordance with newer kernels
> > to use
> > more features by default if people use -cpu z14.
>
> Agreed, this was the original purpose of the default models. Can "break"
> on old kernels, but the compat machines can help for these users, so it
> does not really "break".
That seems fine then.
>
> >
> > Now that I look a 2nd time: shall we also add
> > S390_FEAT_GROUP_MULTIPLE_EPOCH_PTFF ?
>
> I think so.
>
> >
> >
> >>
> >> [It's probably all good, although I like to wait for David's ack for
> >> any cpu model patches :)]
>
> I'm fine with this :)
>
> With S390_FEAT_GROUP_MULTIPLE_EPOCH_PTFF also added
>
> Reviewed-by: David Hildenbrand <da...@redhat.com>
Ok, can I please get a v2 with that added as well?
>
> >>
> >>>
> >>> Machines s390-ccw-virtio-3.1 and older will retain the old CPU
> >>> models and will not provide this bit in the default model.
> >>>
> >>> Signed-off-by: Collin Walling <wall...@linux.ibm.com>
> >>> ---
> >>> hw/s390x/s390-virtio-ccw.c | 1 +
> >>> target/s390x/gen-features.c | 1 +
> >>> 2 files changed, 2 insertions(+)
> >>>
> >>> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> >>> index fd9d0b0542..32c5027345 100644
> >>> --- a/hw/s390x/s390-virtio-ccw.c
> >>> +++ b/hw/s390x/s390-virtio-ccw.c
> >>> @@ -757,6 +757,7 @@ DEFINE_CCW_MACHINE(4_0, "4.0", true);
> >>> static void ccw_machine_3_1_instance_options(MachineState *machine)
> >>> {
> >>> ccw_machine_4_0_instance_options(machine);
> >>> + s390_cpudef_featoff_greater(14, 1, S390_FEAT_MULTIPLE_EPOCH);
> >>> }
> >>>
> >>> static void ccw_machine_3_1_class_options(MachineClass *mc)
> >>> diff --git a/target/s390x/gen-features.c b/target/s390x/gen-features.c
> >>> index 70015eaaf5..d258d67dca 100644
> >>> --- a/target/s390x/gen-features.c
> >>> +++ b/target/s390x/gen-features.c
> >>> @@ -550,6 +550,7 @@ static uint16_t default_GEN14_GA1[] = {
> >>> S390_FEAT_GROUP_MSA_EXT_6,
> >>> S390_FEAT_GROUP_MSA_EXT_7,
> >>> S390_FEAT_GROUP_MSA_EXT_8,
> >>> + S390_FEAT_MULTIPLE_EPOCH,
> >>> };
> >>>
> >>> /* QEMU (CPU model) features */
> >>
> >
>
>
