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

[Michael S. Tsirkin]

On Mon, Jan 12, 2015 at 04:25:01PM +0530, Amit Shah wrote:
> 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

Interesting. So this isn't for the benefit of linux guests then?
Which guests do actually benefit? It might be a good idea to
put this info in the commit log.