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

[Marcel Apfelbaum <marcel@redhat.com>]

On 01/12/2015 12:55 PM, 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 finally found it, acpi_get_pm_info in hw/i386/acpi-build.c
access the object's properties for both pc/q35.

[discussed off-list]
Last thing that is missing is:
   - in ich9_pm_init we have acpi_pm1_cnt_init(&pm->acpi_regs, &pm->io, 2);
   - while in piix4_pm_initfn we have acpi_pm1_cnt_init(&s->ar, &s->io, s->s4_val);

So ich9_pm_init can override the actual object property value, better if we update it
accordingly.

Thanks,
Marcel

>> 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
>