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

From: Andrea Bolognani <abologna@redhat.com>
To: Andrew Jones <ajones@ventanamicro.com>
Cc: "Philippe Mathieu-Daudé" <philmd@linaro.org>,
	"Sunil V L" <sunilvl@ventanamicro.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Alistair Francis" <alistair.francis@wdc.com>,
	"Bin Meng" <bin.meng@windriver.com>,
	qemu-riscv@nongnu.org, qemu-devel@nongnu.org,
	"Anup Patel" <apatel@ventanamicro.com>,
	"Atish Kumar Patra" <atishp@rivosinc.com>,
	"Ani Sinha" <ani@anisinha.ca>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	"Markus Armbruster" <armbru@redhat.com>,
	"Igor Mammedov" <imammedo@redhat.com>,
	"Gerd Hoffmann" <kraxel@redhat.com>,
	"Thomas Huth" <thuth@redhat.com>,
	"Bernhard Beschow" <shentey@gmail.com>
Subject: Re: [PATCH 02/10] hw/riscv/virt: Add a switch to enable/disable ACPI
Date: Tue, 7 Feb 2023 05:56:58 -0800	[thread overview]
Message-ID: <CABJz62M+n4DFqMPttzaDrSRzDcjkyEduX_NAv=-9J58mmUe+Ng@mail.gmail.com> (raw)
In-Reply-To: <20230207102353.hpg2gxh22urjbebu@orel>

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

-- 
Andrea Bolognani / Red Hat / Virtualization