Re: [PATCH v4 2/3] hw/acpi: add indication for i8042 in IA-PC boot flags of the FADT table

[Ani Sinha]

On Wed, Mar 2, 2022 at 6:12 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Wed, Mar 02, 2022 at 10:44:03AM +0530, Ani Sinha wrote:
> > On Wed, Mar 2, 2022 at 12:50 AM Liav Albani <liavalb@gmail.com> wrote:
> > >
> > >
> > > On 3/1/22 11:52, Ani Sinha wrote:
> > > >
> > > > On Tue, 1 Mar 2022, Igor Mammedov wrote:
> > > >
> > > >> On Mon, 28 Feb 2022 22:17:32 +0200
> > > >> Liav Albani <liavalb@gmail.com> wrote:
> > > >>
> > > >>> This can allow the guest OS to determine more easily if i8042 
> > > >>> controller
> > > >>> is present in the system or not, so it doesn't need to do probing of 
> > > >>> the
> > > >>> controller, but just initialize it immediately, before enumerating the
> > > >>> ACPI AML namespace.
> > > >>>
> > > >>> This change only applies to the x86/q35 machine type, as it uses FACP
> > > >>> ACPI table with revision higher than 1, which should implement at 
> > > >>> least
> > > >>> ACPI 2.0 features within the table, hence it can also set the IA-PC 
> > > >>> boot
> > > >>> flags register according to the ACPI 2.0 specification.
> > > >>>
> > > >>> Signed-off-by: Liav Albani <liavalb@gmail.com>
> > > >>> ---
> > > >>>   hw/acpi/aml-build.c         | 11 ++++++++++-
> > > >>>   hw/i386/acpi-build.c        |  9 +++++++++
> > > >>>   hw/i386/acpi-microvm.c      |  9 +++++++++
> > > >> commit message says it's q35 specific, so wy it touched microvm anc 
> > > >> piix4?
> > > > Igor is correct. Although I see that currently there are no 8042 devices
> > > > for microvms, maybe we should be conservative and add the code to detect
> > > > the device anyway. In that case, the change could affect microvms too 
> > > > when
> > > > such devices get added in the future.
> > > >
> > > >
> > > > echo -e "info qtree\r\nquit\r\n" | ./qemu-system-x86_64 -machine microvm
> > > > -monitor stdio 2>/dev/null | grep 8042
> > > >
> > > > <empty>
> > >
> > > What about this?
> > >
> > > echo -e "info qtree\r\nquit\r\n" | qemu-system-x86_64 -machine microvm
> > > -device i8042 -monitor stdio 2>/dev/null | grep 8042
> > >
> > > Or this?
> > >
> > > echo -e "info mtree\r\nquit\r\n" | qemu-system-x86_64 -machine microvm
> > > -device i8042 -monitor stdio 2>/dev/null | grep 8042
> >
> > On both occasions you are explicitly adding the device.
>
> Yes of course.

OK. I did not think for a "microvm" one would explicitly add more 8042
devices beyond what was added by default in the real life use case.