[PATCH 15/15] Revert "x86: default to reboot via ACPI"

Matthew Garrett mjg at redhat.com
Sun Nov 9 05:24:23 EST 2008

On Sun, Nov 09, 2008 at 12:11:03PM +0200, Avi Kivity wrote:
> Matthew Garrett wrote:
> >Hmm. But we're seeing some machines that end up very confused if 
> >rebooted via ACPI. I guess we need to run Vista on them to find out how 
> >they behave. What OSI strings did your KVM setup expose? We know that 
> >Windows changes behaviour under various circumstances depending on which 
> >OS the firmware requests, so it's almost possible that this is another 
> >of those cases.
> >  
> Isn't it the other way around?  The firmware changes behavior depending 
> on how the OS identifies itself?

That also happens, yes.

> Reboot is a fixed feature IIRC, so it cannot change depending on 
> identification strings.

The ID strings that the firmware requests give a good idea about which 
operating systems the machine has been tested with. If Vista uses the 
ACPI method then having the firmware request the OSI string for Vista 
gives us a good indication that it's safe to use the ACPI method.

Matthew Garrett | mjg59 at srcf.ucam.org

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