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

From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH 23/31] ich9: implement SMI_LOCK
Date: Mon, 11 May 2015 17:21:34 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0

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
where I wrote explicitly "Even if the OS tries to maliciously set
APMC_EN to 0 (SMI_LOCK doesn't lock APMC_EN)...".


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