Re: [PATCH] deprecation: x86 default machine types

* Daniel P. Berrangé (berrange(a)redhat.com) wrote: > On Tue, Mar 01, 2022 at 07:54:32PM +0000, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" <dgilbert(a)redhat.com&gt; > > > > Declare the intent to require a machine type to be specified on x86 > > system emulation. > > > > Signed-off-by: Dr. David Alan Gilbert <dgilbert(a)redhat.com&gt; > > --- > > docs/about/deprecated.rst | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > > index 85773db631..143c60d105 100644 > > --- a/docs/about/deprecated.rst > > +++ b/docs/about/deprecated.rst > > @@ -324,6 +324,14 @@ machine is hardly emulated at all (e.g. neither the LCD nor the USB part had > > been implemented), so there is not much value added by this board. Use the > > ``ref405ep`` machine instead. > > > > +x86 default machine type > > +'''''''''''''''''''''''' > > + > > +x86 currently defaults to the ```pc``` machine type which is based on the very > > +old ```i440fx``` chipset. This default will be removed and the user will be > > +required to specify a machine type explicitly using -M; users are encouraged to > > +switch to the not quite as old ```q35``` machine types. > > This will have no impact on anyone using libvirt as a mgmt app, > because it will explicitly set 'pc' if the user doesn't request > a machine type. > > It will, however, break a huge number of users who don't use > libvirt or a similar mgmt app. > > 'q35' is not a drop in replacement for 'pc', and even though > it is slightly newer, the features it brings are not likely > to be important enough for most users who aren't using a mgmt > app to care about switching. I can see it having advantages for those who do things like PCIe pass through of graphics cards. However, my main concern is that there's a split happening where downstream we're working primarily on q35 but a lot of people still use i440fx; eventually that split will mean the i440fx users will have a pretty bad experience instability/features. So I'd like to encourage them onto a35.

> In the ongoing work to introduce a completely new system > emulator binary that is exclusively runtime QMP configured, > the machine type will almost certainly be mandatory, without > affecting existing users. That would also apply consistently > across all target arches. I'm assuming that will also cause the disruption to those end users.