Re: [Qemu-devel] RFC: ACPI, HPET._CRS, MacOSX vs. WinXP

[Michael S. Tsirkin]

On Mon, Jan 20, 2014 at 01:16:02PM +0100, Paolo Bonzini wrote:
> Il 20/01/2014 13:08, Michael S. Tsirkin ha scritto:
> >>> > > 
> >>> > > I think the hack looking for the SMC device is safer than _OSI: OSPMs
> >>> > > are known to do crazy things when they see _OSI, such as assuming they
> >>> > > need to try and emulate the OS probed.
> >> > 
> >> > Source?
> >> > 
> >> > Paolo
> > For example, this one
> > http://article.gmane.org/gmane.comp.bios.coreboot.seabios/7235
> 
> No, not source code.
> 
> Source for "OSPMs do crazy things when they see _OSI".
> 
> Paolo

Ah, that one.

For example, this msdn article at microsoft.com:
http://msdn.microsoft.com/en-us/library/windows/hardware/gg463275.aspx
"How to Identify the Windows Version in ACPI by Using _OSI"

at the end it states:
        the operating system makes features available based on the
        string argument to the _OSI method.


The ACPI spec states this in a more verbose form:
5.7.2 _OSI (Operating System Interfaces)

         OSPM can choose to expose new functionality
        based on the _OSI argument string. That is, OSPM can use the strings
        passed into _OSI to ensure
        compatibility between older platforms and newer operating systems by
        maintaining known
        compatible behavior for a platform.


The concern therefore is that if bios only queries
OSI for Darwin and not other OSes, some OSPM will assume
it's a macbook hardware and do something stupid.

-- 
MST