Re: [PATCH 02/10] hw/riscv/virt: Add a switch to enable/disable ACPI

[Thomas Huth]

On 07/02/2023 14.56, Andrea Bolognani wrote:
> On Tue, Feb 07, 2023 at 11:23:53AM +0100, Andrew Jones wrote:
> > On Mon, Feb 06, 2023 at 12:18:06PM +0100, Philippe Mathieu-Daudé wrote:
> > > On 6/2/23 11:54, Andrea Bolognani wrote:
> > > > On Thu, Feb 02, 2023 at 10:22:15AM +0530, Sunil V L wrote:
> > > > > +    object_class_property_add(oc, "acpi", "OnOffAuto",
> > > > > +                              virt_get_acpi, virt_set_acpi,
> > > > > +                              NULL, NULL);
> > > > > +    object_class_property_set_description(oc, "acpi",
> > > > > +                                          "Enable ACPI");
> > > >
> > > > The way this works on other architectures (x86_64, aarch64) is that
> > > > you get ACPI by default and can use -no-acpi to disable it if
> > > > desired. Can we have the same on RISC-V, for consistency?
> > >
> > > -no-acpi rather seems a x86-specific hack for the ISA PC machine, and
> > > has a high maintenance cost / burden.
> >
> > Can you elaborate on this? RISCV doesn't need '-no-acpi' specifically.
> > If -no-acpi is problematic for some reason, then something like
> > '-machine virt,acpi=off' would be sufficient for switching to DT too.
>
> I would greatly prefer it if the command line interface could be kept
> consistent across architectures.
>
> It looks like i440fx and q35 both have an 'acpi' machine property. Is
> -no-acpi just sugar for acpi=off?

Yes, it is, see softmmu/vl.c:

            case QEMU_OPTION_no_acpi:
                qdict_put_str(machine_opts_dict, "acpi", "off");
                break;

> Is it considered desirable to get rid of -no-acpi?

Sounds like a good idea, indeed!

> If so, we should follow the usual deprecation
> process and get rid of it after libvirt has had a chance to adapt.
>
> In the scenario described above, it would make sense for RISC-V to
> only offer the machine type option (assuming that -no-acpi doesn't
> come for free with that) instead of putting additional effort into
> implementing an interface that is already on its way out.

I agree. IMHO the machine parameter should be enough, no need to introduce 
"-no-acpi" here.

 Thomas