* Daniel P. Berrangé (berrange@xxxxxxxxxx) wrote: > On Wed, Mar 02, 2022 at 07:38:52PM +0000, Dr. David Alan Gilbert wrote: > > * Daniel P. Berrangé (berrange@xxxxxxxxxx) wrote: > > > On Tue, Mar 01, 2022 at 07:54:32PM +0000, Dr. David Alan Gilbert (git) wrote: > > > > From: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx> > > > > > > > > Declare the intent to require a machine type to be specified on x86 > > > > system emulation. > > > > > > > > Signed-off-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx> > > > > --- > > > > 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. > > We've still got quite significant testing coverage of i440fx and outside > of PCI-Express much logic is shared with q35. Right now at least i440fx > feels mature and stable, while q35 is still showing significant > instability with PCI-Express and hotplug in particular. I'd hoppe at > least the combination of maturity of our plain PCI code and testing > coverage would address risk of significant regressions in i440fx even > when attention is on q35. OK, lets drop this for now. > > > 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. > > The difference is that people would opt-in to usage of the new system > binaries. So existing users, scripts and documentation won't be impacted > unless they decide to switch - at least as long as we keep the old > system emulators around. If did eventually decide to remove the old > binaries, then there would be disruption but that's more of a clean > break with the past. So I guess that when this happens people will be pushed to the new binaries and the old ones will degrade reasonably fast. Dave > Regards, > Daniel > -- > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| > -- Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK
