Re: [PATCH for-7.0] i386: Deprecate the -no-hpet QEMU command line option

On Mon, Dec 06, 2021 at 10:02:44 +0100, Thomas Huth wrote: > On 06/12/2021 09.57, Peter Krempa wrote: >> On Mon, Dec 06, 2021 at 09:47:58 +0100, Thomas Huth wrote: >>> On 06/12/2021 09.40, Thomas Huth wrote: >>>> The HPET setting has been turned into a machine property a while ago >>>> already, so we should finally do the next step and deprecate the >>>> legacy CLI option, too. >>>> While we're at it, add a proper help text for the machine property, too. >>>> >>>> Signed-off-by: Thomas Huth <thuth(a)redhat.com&gt; >>>> --- >>>> docs/about/deprecated.rst | 6 ++++++ >>>> hw/i386/pc.c | 2 ++ >>>> qemu-options.hx | 2 +- >>>> softmmu/vl.c | 1 + >>>> 4 files changed, 10 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst >>>> index 5693abb663..1dfe69aa6a 100644 >>>> --- a/docs/about/deprecated.rst >>>> +++ b/docs/about/deprecated.rst >>>> @@ -198,6 +198,12 @@ form is preferred. >>>> Using ``-drive if=none`` to configure the OTP device of the sifive_u >>>> RISC-V machine is deprecated. Use ``-drive if=pflash`` instead. >>>> +``-no-hpet`` (since 7.0) >>>> +'''''''''''''''''''''''' >>>> + >>>> +The HPET setting has been turned into a machine property. >>>> +Use ``-machine hpet=off`` instead. >>> [...] >>> >>> Forgot to CC: the libvirt folks, doing so now. >>> >>> Seems like libvirt is still using -no-hpet in some few spots, so I guess >>> these would need to be changed first, before we could finally remove this >>> option in QEMU? >> >> Yes we need to switch to the new property first. >> >> Is the new way via -machine property by any chance usable with >> qemu-2.11? If yes, then we can do it unconditionally, otherwise we'll >> need a witness to detect the support for the new flag as a qemu >> capability. > > The machine property has been added just a year ago: > > https://gitlab.com/qemu-project/qemu/-/commit/0259c78ca79 > > So it's just available on QEMU v5.2.0 and newer. Okay, so we can't unfortunately always use the new way. I had a brief look in what libvirt queries to build the capability list and unfortunately neither query-command-line-options nor query-machines list anything which we could detect. Since only the config knob is changing the presence in qom-list-types doesn't help either. So if qemu want's to deprecate the '-no-hpet' spelling we need something which we can detect by one of the above means or other probe command to use the new spelling.