On Mon, Feb 20, 2023 at 11:36:36AM +0100, Laszlo Ersek wrote:
> On 2/17/23 12:44, Richard W.M. Jones wrote:
> > As with the prior commit, prefer -cpu host for all guests (except when
> > we have more information from the source hypervisor). Although there
> > is the disadvantage that -cpu host is non-migratable, in practice it
> > would be very difficult to live migrate a host launched using direct
> > qemu commands.
> >
> > Note that after this change, gcaps_arch_min_version is basically an
> > informational field. No output uses it, but it will appear in debug
> > output and there's the possibility we might use it for a future output
> > mode.
> >
> > Thanks: Laszlo Ersek
> > ---
> > lib/types.mli | 6 +++++-
> > output/output_qemu.ml | 6 +-----
> > 2 files changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/lib/types.mli b/lib/types.mli
> > index 743daa8a14..4a183dd3ae 100644
> > --- a/lib/types.mli
> > +++ b/lib/types.mli
> > @@ -268,7 +268,11 @@ type guestcaps = {
> > minimum version. Notably RHEL >= 9 requires at least x86_64-v2.
> >
> > If the guest is capable of running on QEMU's default VCPU model
> > - for the architecture ([-cpu qemu64]) then this is set to [0]. *)
> > + for the architecture ([-cpu qemu64]) then this is set to [0].
> > +
> > + Note this capability is not actually used by any current output
> > + mode. It is retained in case we might use it in future, but we
> > + might remove it if it is not used. *)
> >
> > gcaps_virtio_1_0 : bool;
> > (** The guest supports the virtio devices that it does at the virtio-1.0
> > diff --git a/output/output_qemu.ml b/output/output_qemu.ml
> > index 491906ebf9..2bbacb6eda 100644
> > --- a/output/output_qemu.ml
> > +++ b/output/output_qemu.ml
> > @@ -175,11 +175,7 @@ module QEMU = struct
> >
> > arg "-m" (Int64.to_string (source.s_memory /^ 1024L /^ 1024L));
> >
> > - (match source.s_cpu_model, guestcaps.gcaps_arch_min_version with
> > - | None, 0 -> ()
> > - | None, _ -> arg "-cpu" "host"
> > - | Some model, _ -> arg "-cpu" model
> > - );
> > + arg "-cpu" (Option.default "host" source.s_cpu_model);
>
> (Ah yes, we have our own Option module from
> common/mlstdutils/std_utils.ml*, not the "standard" one
> <https://v2.ocaml.org/api/Option.html>.)
We should switch to using the standard one, but in this case it
depends on OCaml 4.08. RHEL 7 has OCaml 4.05 and RHEL 8 has
OCaml 4.07.
Nevertheless I checked now if our module is needlessly different from
the official one and there are a few things so it's worth slowly
converging ours to make it easier to drop in future and reduce
surprises.
> > if source.s_vcpu > 1 then (
> > (match source.s_cpu_topology with
>
> Reviewed-by: Laszlo Ersek <[email protected]>
Thanks,
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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