Comment # 19 on bug 961853 from Gary Ching-Pang Lin

(In reply to Andreas Taschner from comment #18)
> (In reply to Gary Ching-Pang Lin from comment #17)
> > (In reply to James Fehlig from comment #14)
> > > I noticed 3 while testing the fixes for 1 and 2. Some settings are persisted
> > > (e.g. Device Manager -> OVMF Platform Configuration -> Preferred
> > > Resolution), while others are not (e.g. Boot Maintenance Manager -> Set Time
> > > Out Value).  It seems like a problem in ovmf. When saving changes in the
> > > firmware UI, the VARS file access time is updated, so something was written
> > > to the file. But in the case of "Time Out Value", simply going to the top
> > > level menu then back to Set Time Out Value is enough to lose the setting.
> > > Power-cycling the VM also resets the "Time Out Value" to 0. Gary, does that
> > > sound like and ovmf issue to you?
> 
> I appreciate the confirmation of my findings :-)
>  
> > I checked OVMF and the timeout actually relies on fwcfg from qemu, i.e.
> > -boot menu=off/on, not any UEFI variable. The menu of Boot Maintenance
> > Manager is a general menu for different platforms, and OVMF happens to
> > ignore the option.
> 
> Can you help me understand this, please. Is it so that the Time Out Value in
> the Boot Maintenance Manager menu is of no use ?
> We will (at least in case OVMF gets supported on SLES) inevitably run into
> support inquiries when customers try changing the value and observe the same
> as us. In my opinion an option should either work or not be there. At the
> very least the "context-hint" text on the right side of the screen should
> inform that the option has no effect on virtual setups (IIUC).... which then
> leads to the question why is it then there ? 
> Please forgive if I am missing (parts of) the concept, being a complete
> novice on UEFI.
OVMF is a subproject of edk2(*) which is a reference implementation of UEFI.
There are a lot of "Pkg"s in the project and most of Pkgs are
platform-independent. Taking "Boot Maintenance Manager" for example, it's in
BdsDxe in IntelFrameworkModulePkg and provides a general menu and options.
Whether the option works or not, it depends on the implementation of the
underlying platform. Although BdsDxe did write the TimeOut value to a UEFI
variable, "TimeOut", it seems OVMF just ignored the variable. From my point of
view, it's something not implemented in OVMF upstream. It only affects how long
the firmware would hold before loading the bootloader and is not an important
feature. Besides, the user can change the value from QEMU instead of clicking
into the menu. I guess OVMF upstream doesn't really care this variable.

(*) http://www.tianocore.org/edk2/