Re: [flashrom] Fwd: BIOS Write Enable bit problem.

[Andrew Goodbody]

On 08/02/13 23:47, Rich Futyma wrote:
> Does anyone know why bit 0 in the BIOS Control register cannot be set using
> Intel® X79 Express Chipset. This is what I get when running:
> flashrom -r /tmp/bios.rom -p internal or  flashrom -w xx.rom -p internal
>
> *Warning: Setting Bios Control at 0xdc from 0x2a to 0x0b on X79 failed.*
> *New value is 0x2a.*

You can see that bit 1 is already set. This will generate an SMI when 
you attempt to set bit 0. There will be SMM code that will reset bit 0 
if you have not performed the correct handshake beforehand. This is a 
protection mechanism to prevent unauthorised modification of the BIOS.

Andrew

Fwd: BIOS Write Enable bit problem.

[Rich Futyma]

Andrew,

Would happen to know which linux driver handles this interrupt?

Also, do you know where is this "correct handshake" described? It seems
that once bit 1 is set it can only be cleared by the reset.
----
rich

On Sat, Feb 9, 2013 at 5:34 PM, Andrew Goodbody wrote:
> On 08/02/13 23:47, Rich Futyma wrote:
> > Does anyone know why bit 0 in the BIOS Control register cannot be set
> > using
> > Intel® X79 Express Chipset. This is what I get when running:
> > flashrom -r /tmp/bios.rom -p internal or  flashrom -w xx.rom -p internal
> >
> > *Warning: Setting Bios Control at 0xdc from 0x2a to 0x0b on X79 failed.*
> > *New value is 0x2a.*
>
> You can see that bit 1 is already set. This will generate an SMI when you
> attempt to set bit 0. There will be SMM code that will reset bit 0 if you
> have not performed the correct handshake beforehand. This is a protection
> mechanism to prevent unauthorised modification of the BIOS.
>
> Andrew

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