Re: [Qemu-devel] [PATCH 3/3] Get system state configuration from QEMU and patch DSDT with it.

[Gleb Natapov]

On Sun, May 20, 2012 at 02:44:51PM +0300, Avi Kivity wrote:
> On 05/20/2012 12:03 PM, Gleb Natapov wrote:
> > QEMU may want to disable guest's S3/S4 support and it wants to distinguish
> > between regular powerdown and S4 powerdown. To support that new fw_cfg
> > option was added that passes supported system states and what value should
> > guest use to enter each state. States are passed in 6 byte array. Each
> > byte represents one system state. If byte at offset X has its MSB set
> > it means that system state X is supported and to enter it guest should
> > use the value from lowest 7 bits. Patch also detects old QEMU and uses
> > values that work in backwards compatible way there.
> >
> 
> 
> Do we actually have to patch the DSDT?  Or can _S3 etc be made into
> functions instead? (and talk to the bios, or even to fwcfg directly?)
> 
We better not talk to fwcfg after OSPM is started since this is firmware
confing interface. Regardless, presence of _S3 name or method is all
that needed for OS enabling S3 option. If _S3 is defined as a method it
has to return Package() otherwise iasl refuses to compile it.

--
                        Gleb.