[virt-tools-list] [virt-manager PATCH 5/5] virt-manager: add a new guest feature GIC for AMR guests

[Cole Robinson]

Okay, I need to finally truly figure out how all this stuff fits together to
try and understand if it makes sense to expose in the GUI. My understanding is
that there's 4 pieces of info at play here:

- What gic versions can qemu emulate? (available for domain type=qemu)
- What gic versions does the host support? (available for domain type=kvm)
- What gic versions does the guest OS support? (eventually tracked by libosinfo)

As of now there's currently only 3 possible GIC settings: version=2,
version=3, version=host (kvm only, basically like -cpu host)

Libvirt will default to the highest gic version that qemu advertises support
for. That will be gic v2 for type=qemu (the only version qemu presently
emulates), and whatever the host supports for type=kvm

That's basically the extent of my knowledge, so I'd like to know:

- does gic emulation have any impact on type=kvm, or is it only relevant to
type=qemu? (I assume the latter)
- do aarch64 hosts only support one gic version, or does say a v3 host also
support v2?
- do guest OS support multiple gic versions? like does a guest OS that
supports v3 also support v2? if a guest OS doesn't support a gic version, does
that mean it completely fails to boot, or some other failure scenario?
- what gic versions to common guest OS support? rhelsa, fedora 22, 23, 24 etc.
- besides the OS compat issue, what does gic v3 vs v2 actually provide?
something super critical for install time?
- is gic setting something that can be changed later without guest impact?

I'm trying to answer the question 'when do users want to change that default',
outside of obvious dev/testing scenarios. If there isn't presently, or planned
for the near future, a critical case where the user needs to change the
default just to get a booting/installing VM, then I'd rather not put this in
the GUI and just save it for virt-install/virt-xml

Thanks,
Cole

On 06/10/2016 01:30 PM, Pavel Hrdina wrote:
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1334857
> 
> Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> ---
>  ui/details.ui          | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  virtManager/details.py | 36 ++++++++++++++++++++++++++++++++++-
>  virtManager/domain.py  |  8 +++++++-
>  3 files changed, 93 insertions(+), 2 deletions(-)
> 
> diff --git a/ui/details.ui b/ui/details.ui
> index 4159f1d..953bd00 100644
> --- a/ui/details.ui
> +++ b/ui/details.ui
> @@ -1200,6 +1200,57 @@ if you know what you are doing.</small></property>
>                                              <property name="top_attach">3</property>
>                                            </packing>
>                                          </child>
> +                                        <child>
> +                                          <object class="GtkLabel" id="overview-gic-title">
> +                                            <property name="visible">True</property>
> +                                            <property name="can_focus">False</property>
> +                                            <property name="valign">start</property>
> +                                            <property name="label" translatable="yes">_GIC version:</property>
> +                                            <property name="use_underline">True</property>
> +                                            <property name="ellipsize">middle</property>
> +                                            <property name="angle">0.089999999999999997</property>

Looks like your mouse wheel probably hit the 'angle' field :)

- Cole