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Re: [Qemu-devel] [PATCH 2/2] pc: reject do pc_acpi_init if acpi_enabled

From: li guang
Subject: Re: [Qemu-devel] [PATCH 2/2] pc: reject do pc_acpi_init if acpi_enabled is false
Date: Thu, 16 May 2013 08:14:36 +0800

在 2013-05-15三的 15:44 +0200,Laszlo Ersek写道:
> On 05/15/13 10:54, li guang wrote:
> > 在 2013-05-15三的 10:38 +0200,Paolo Bonzini写道:
> >> Il 15/05/2013 06:01, liguang ha scritto:
> >>> Signed-off-by: liguang <address@hidden>
> >>
> >> --verbose, please.
> >>
> >> What problem does this patch fix?
> > 
> > Oh, sorry to be lazy ...
> > QEMU's option '-no-acpi' seems does not play
> > a correct role, even started with this, 
> > ACPI tables will also be embedded into BIOS, 
> > and there's no different between with or without it
> > for q35, as i can see.
> > 
> > here, I'm assuming '-no-acpi' is to disable ACPI.
> -no-acpi disables a block of code in pc_init1() [hw/i386/pc_piix.c],
> namely piix4_pm_init() and smbus_eeprom_init().
> pc_acpi_init() loads / exports a default DSDT for the boot firmware. If
> the -acpitable switch is passed, then that code doesn't run.

Yes, if '-acpitable' & '-no-acpi' passed, I think QEMU is valid to
override '-no-acpi' by '-acpitable'.

> I think disabling PM but keeping the default DSDT from SeaBIOS is a
> valid use case; the DSDT seems to contain a bunch of non-PM
> functionality (see src/acpi-dsdt*.dsl in SeaBIOS). The "-no-acpi" switch
> is likely a misnomer (it should say "-no-acpi-pm" or some such), but in
> any case I believe it should not prevent exporting the DSDT.

what's the purpose of only disable PM by '-no-acpi'?
can we use -no-acpi to disable whole ACPI?


> Currently you can prevent exporting the default DSDT for example with:
>   -acpitable sig=NONE,data=/dev/null
> This will export a table with signature NONE, otherwise qemu-default
> ACPI table headers, and no table contents. It will also prevent
> pc_acpi_init() from running. See "AcpiTableOptions" in
> "qapi-schema.json" and "hw/acpi/core.c".
> Thanks,
> Laszlo

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