Re: [Qemu-devel] [PATCH 1/1] ich9: add disable_s3, disable_s4, s4_val properties

[Amit Shah]

On (Mon) 12 Jan 2015 [12:26:08], Marcel Apfelbaum wrote:
> On 12/16/2014 01:23 PM, Amit Shah wrote:
> >PIIX4 has disable_s3 and disable_s4 properties to enable or disable PM
> >functions.  Add such properties to the ICH9 chipset as well for the Q35
> >machine type.
> >
> >S3 / S4 are not guaranteed to always work (needs work in the guest as
> >well as QEMU for things to work properly), and disabling advertising of
> >these features ensures guests don't go into zombie state if something
> >isn't working right.
> >
> >The defaults are kept the same as in PIIX4: both S3 and S4 are enabled
> >by default.
> >
> >These can be disabled via the cmdline:
> >
> >   ... -global ICH9-LPC,disable_s3=1 -global ICH9-LPC,disable_s4=1
>                         ^^^                           ^^^
> Should be -global ICH9-LPC.disable_s3=1 -global ICH9-LPC.disable_s4=1

Indeed, thanks.

> Hi Amit, thanks for answering my prev question.
> I have one more:)
> 
> I didn't see how the properties are connected to the ACPI mechanism.
> I tested it with your suggested command line and it didn't work from some 
> reason.
>    - I used ... -M Q35 -global ICH9-LPC.disable_s3=1 -global 
> ICH9-LPC.disable_s4=1
>    - On guest: pm-is-supported --hibernate && echo $? => 0 (enabled)
>    - Furthermore, pm-hibernate worked
> 
> Maybe I am missing something or maybe this is not in the scope of this patch.

Hibernate is special for Linux guests.  If acpi-based hibernate isn't
available, Linux simulates it by writing a hibernate image and doing a
shutdown of the guest instead of entering the S4 state.

To test, there are two ways: check if s3 works after passing this
parm, or check the acpi blobs inside the guest for the advertisement
of the params.

                Amit