Re: [Qemu-devel] [PATCH 23/31] ich9: implement SMI_LOCK

[Paolo Bonzini]

On 11/05/2015 17:17, Laszlo Ersek wrote:
> If I understand correctly, this makes SMI_LOCK lock down the GBL_SMI_EN
> bit (and my OVMF patch that relies on that / tests it is satisfied too).
> 
> But, it doesn't seem to lock down APMC_EN. According to the ICH9 spec,
> it doesn't need to -- however when we discussed this earlier (see
> Message-Id: <address@hidden>), the idea was to lock down
> APMC_EN as well. (And I don't understand why the ICH9 spec / hw
> implementation doesn't lock APMC_EN; without that, APM_CNT won't
> necessarily trigger an SMI.)

I don't think it should.  See here
<https://lists.gnu.org/archive/html/qemu-devel/2015-04/msg02758.html>
where I wrote explicitly "Even if the OS tries to maliciously set
APMC_EN to 0 (SMI_LOCK doesn't lock APMC_EN)...".

Paolo