linux-kernel - Re: [tip:x86/urgent] x86/microcode/intel: Disable late loading on model 79

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Date:   Sat, 30 Dec 2017 17:38:58 -0000
From:   sonofagun@...nmailbox.org
To:     linux-kernel@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86/microcode/intel: Disable late loading on model 79

I suppose it is for Broadwell EX(Expandable or Expensive, whichever you like). The patch description is wrong!
Document 334165-010US describes erratum BDF90:

Loading Microcode Updates or Executing an Authenticated Code Module May Result
in a System Hang

I have not read such a bug in the past. I only knew that AMD K7 could not get microcode updates at all.
Broadwell EX must not have their microcode updated because loading it will cause an UE if the microcode has signature less than 0x0b000021.
I will check what is the signature of the latest update supplied by intel for this model just out of curiosity.

This patch does not check microcode signature, it disables all updates. Is that intentional?