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

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

[Thomas Huth]

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@redhat.com>
---
 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.
+
 
 QEMU Machine Protocol (QMP) commands
 ------------------------------------
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index a2ef40ecbc..0ab6e67afe 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1743,6 +1743,8 @@ static void pc_machine_class_init(ObjectClass *oc, void *data)
 
     object_class_property_add_bool(oc, "hpet",
         pc_machine_get_hpet, pc_machine_set_hpet);
+    object_class_property_set_description(oc, "hpet",
+        "High precision event timer emulation");
 
     object_class_property_add_bool(oc, "default-bus-bypass-iommu",
         pc_machine_get_default_bus_bypass_iommu,
diff --git a/qemu-options.hx b/qemu-options.hx
index ae2c6dbbfc..7b921fcbe3 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2436,7 +2436,7 @@ DEF("no-hpet", 0, QEMU_OPTION_no_hpet,
     "-no-hpet        disable HPET\n", QEMU_ARCH_I386)
 SRST
 ``-no-hpet``
-    Disable HPET support.
+    Disable HPET support. Deprecated, use '-machine hpet=off' instead.
 ERST
 
 DEF("acpitable", HAS_ARG, QEMU_OPTION_acpitable,
diff --git a/softmmu/vl.c b/softmmu/vl.c
index 620a1f1367..471ed006eb 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -3418,6 +3418,7 @@ void qemu_init(int argc, char **argv, char **envp)
                 qdict_put_str(machine_opts_dict, "acpi", "off");
                 break;
             case QEMU_OPTION_no_hpet:
+                warn_report("-no-hpet is deprecated, use '-machine hpet=off' instead");
                 qdict_put_str(machine_opts_dict, "hpet", "off");
                 break;
             case QEMU_OPTION_no_reboot:
-- 
2.27.0

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

[Thomas Huth]

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@redhat.com>
> ---
>   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?

  Thomas

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

[Peter Krempa]

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@redhat.com>
> > ---
> >   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.

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

[Thomas Huth]

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@redhat.com>
>>> ---
>>>    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.

  Thomas

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

[Peter Krempa]

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@redhat.com>
> > > > ---
> > > >    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.

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

[Thomas Huth]

On 06/12/2021 10.19, Peter Krempa wrote:
> 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@redhat.com>
>>>>> ---
>>>>>     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.

I just had another chat with Peter on IRC, and seems like it could be 
detected by running "qom-list-properties" on e.g. the "generic-pc-machine" 
object. However, libvirt does not have that information in their test data 
yet, so it's not a very trivial change to support this in libvirt.
Thus, please don't merge this patch yet, it will currently cause more hassle 
than benefit.

  Thomas

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

[Daniel P. Berrangé]

On Mon, Dec 06, 2021 at 10:44:50AM +0100, Thomas Huth wrote:
> On 06/12/2021 10.19, Peter Krempa wrote:
> > 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@redhat.com>
> > > > > > ---
> > > > > >     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.
> 
> I just had another chat with Peter on IRC, and seems like it could be
> detected by running "qom-list-properties" on e.g. the "generic-pc-machine"
> object. However, libvirt does not have that information in their test data
> yet, so it's not a very trivial change to support this in libvirt.

It is mostly just a tedious matter of getting sample QMP replies for
the qom-list-properties command on various older QEMU versions to
make sure our test suite does the right thing.

> Thus, please don't merge this patch yet, it will currently cause more hassle
> than benefit.

I don't see any problem in QEMU going ahead with this. If it is deprecated
in 7.0, then it won't be until 7.2 that its deleted, which is Dec 2022
timeframe. A year is enough time for libvirt to adapt.

Regards,
Daniel
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