BIOS password...: probably on latitudes only

Lance Haig lnhaig at
Wed Jul 23 04:32:44 CDT 2008

Hi Mario,

Do you think this problem would cause a machine to hard reset and restart?

I am trying to find out why if I start a vm with qemu-kvm it resets the 



Mario Limonciello wrote:
> Andrea:
> I've uploaded 4 fixes that were all attached to that bug that are being
> processed right now.  If you (and anyone else that has encountered this
> problem) could follow the directions on
> to update to the newer libsmbios and HAL packages and then comment on
> that bug, that would be most appreciated.  After some positive feedback
> is received with the new packages, they can be pushed to all machines.
> A little background about the solution:
> The current method of changing the backlight uses a BIOS call to
> actually perform this backlight change on Linux.  On Windows, this
> function isn't stubbed out at all per my understanding.  The ambient
> light sensors of the laptop may be activated in Windows, but any
> adjustments to the backlight are either done physically by pressing the
> up and down buttons for the backlight or by the BIOS without interaction
> with Windows.  On the Linux side, since these functions actually got
> stubbed out, there is software support for changing the backlight.  The
> BIOS can not be written to however, unless an authentication token is
> obtained.  This token gets obtained by providing a user or admin BIOS
> password.
> What I did was provided another method to libsmbios that queries
> directly if there is a type of password present.  I then added a check
> to HAL to see if there is a BIOS password.  If there is, any attempts to
> write to the backlight will not actually make the call into libsmbios,
> but just return.  This will prevent the "lockups" that were encountered
> when multiple calls to change the backlight were happening w/o valid
> tokens.  Those were caused because making a query to change the BIOS
> multiple times appeared to invoke an interrupt handler.
> All in all, the negative side effect to this solution will be the fact
> that any software utilities that would change the backlight won't work
> when you have a BIOS password set.  They didn't work before either
> though, so I don't see this as a regression.
> Regards,
> Andrea Ratto wrote:
>> probably happens on latitudes (d series?) only...
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