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Re: [PATCH 3/3] x86: Switch to q35 as the default machine type
From: |
Michael S. Tsirkin |
Subject: |
Re: [PATCH 3/3] x86: Switch to q35 as the default machine type |
Date: |
Thu, 17 Feb 2022 02:52:05 -0500 |
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 (berrange@redhat.com) wrote:
> > > On Wed, Feb 16, 2022 at 05:40:44PM +0000, Dr. David Alan Gilbert wrote:
> > > > * Thomas Huth (thuth@redhat.com) wrote:
> > > > > On 16/02/2022 12.01, Dr. David Alan Gilbert wrote:
> > > > > > * Gerd Hoffmann (kraxel@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
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, (continued)
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Daniel P . Berrangé, 2022/02/15
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Dr. David Alan Gilbert, 2022/02/15
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Gerd Hoffmann, 2022/02/16
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Dr. David Alan Gilbert, 2022/02/16
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Daniel P . Berrangé, 2022/02/16
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Thomas Huth, 2022/02/16
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Dr. David Alan Gilbert, 2022/02/16
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Daniel P . Berrangé, 2022/02/16
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Dr. David Alan Gilbert, 2022/02/16
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Thomas Huth, 2022/02/17
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type,
Michael S. Tsirkin <=
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Daniel P . Berrangé, 2022/02/17
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Dr. David Alan Gilbert, 2022/02/17
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Thomas Huth, 2022/02/17
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Gerd Hoffmann, 2022/02/17
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Michael S. Tsirkin, 2022/02/17
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Daniel P . Berrangé, 2022/02/17
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Igor Mammedov, 2022/02/17
- Re: [PATCH 3/3] x86: Switch to q35 as the default machine type, Kashyap Chamarthy, 2022/02/17
[PATCH 1/3] tests/x86: Use 'pc' machine type for old hardware tests, Dr. David Alan Gilbert (git), 2022/02/15
[PATCH 2/3] tests/x86: Use 'pc' machine type for hotplug tests, Dr. David Alan Gilbert (git), 2022/02/15