Re: [Qemu-devel] [PATCH 1/2] q35: implement SMRAM.D_LCK

[Paolo Bonzini]

On 15/04/2015 15:58, Gerd Hoffmann wrote:
> The "A Tour Beyond BIOS Implementing S3 Resume with EDKII" white paper
> lists "Lock SMM. This must be done to maintain SMM integrity." as todo
> list item for the edk2 resume code path (page 18).
> 
> So it seems to me it is the job of the firmware to re-lock smm after S3
> (and before handing control back to the OS, obviously).

Right, however "D_LCK can be set to 1 via a normal configuration space
write but can only be cleared by a Full Reset."  A Full Reset is the
PLTRST# pin, which is asserted by the south bridge during power-up and
during CF9h reset.  S3 doesn't seem to be included.

My reading of the EDK2 whitepaper is that this may vary for other chipsets.

Paolo