On Thu, Feb 17, 2022 at 08:46:55AM +0100, Thomas Huth wrote: > On 16/02/2022 18.57, Dr. David Alan Gilbert wrote: > > * Daniel P. Berrangé (berra...@redhat.com) wrote: > > > On Wed, Feb 16, 2022 at 05:40:44PM +0000, Dr. David Alan Gilbert wrote: > > > > * Thomas Huth (th...@redhat.com) wrote: > > > > > On 16/02/2022 12.01, Dr. David Alan Gilbert wrote: > > > > > > * Gerd Hoffmann (kra...@redhat.com) wrote: > > > > > > > Hi, > > > > > > > > Given the semantic differences from 'i440fx', changing the > > > > > > > > default > > > > > > > > machine type has effects that are equivalent to breaking command > > > > > > > > line syntax compatibility, which is something we've always tried > > > > > > > > to avoid. > > > > > > > > > > > > > > And if we are fine breaking backward compatibility I'd rather > > > > > > > *not* pick > > > > > > > a default, effectively making -M $something mandatory, similar to > > > > > > > arm. > > > > > > > > > > > > Oh, that's probably easy to do; what are other peoples thoughts on > > > > > > that? > > > > > > > > > > I agree with Gerd. Getting rid of a default machine on x86 is likely > > > > > better > > > > > than silently changing it to q35. But I'd maybe say that this should > > > > > go > > > > > through the deprecation process first? > > > > > > > > So just adding something like the following under 'System emulator > > > > machines': > > > > > > > > x86 default machine type > > > > ------------------------ > > > > > > > > x86 currently defaults to the very old ```pc``` machine type > > > > which is based on the very old ```i440f``` 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 option is going to take a lot more work switching all the > > > > test cases over; in my world here I'd only changed the tests that broke > > > > on q35, now everything is going to need to specify a type). > > > > > > ....which is still nothing compared to how many users will be impacted > > > and the docs all over the internet we'll never be able to change, which > > > give illustrations using qemu command lines without '-M pc' > > > > What's your prreference - it sounds like you'd prefer to leave the > > default as 'pc' ? > > > > aarch's message is: > > qemu-system-aarch64: No machine specified, and there is no default > > Use -machine help to list supported machines > > > > We could add a: > > 'Use -machine pc for the old default behaviour' > > Sounds like a good idea, but then I'd also do: > > 'Use -M pc for the old default behaviour, or -M q35 for a more modern > machine' or so. > > Thomas >
How about we start by going through a deprecation period then? Make attempts to create a machine without -machine produce a warning for a couple of cycles. -- MST
