linux-kernel - Re: [PATCH] x86/microcode: Add an option to reload microcode even if revision is unchanged

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Date:   Wed, 4 Sep 2019 17:21:32 -0700
From:   "Raj, Ashok" <ashok.raj@...el.com>
To:     Boris Petkov <bp@...en8.de>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Mihai Carabas <mihai.carabas@...cle.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jon Grimm <Jon.Grimm@....com>, kanth.ghatraju@...cle.com,
        konrad.wilk@...cle.com, patrick.colp@...cle.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        x86-ml <x86@...nel.org>, linux-kernel@...r.kernel.org,
        Ashok Raj <ashok.raj@...el.com>
Subject: Re: [PATCH] x86/microcode: Add an option to reload microcode even if
 revision is unchanged

On Thu, Sep 05, 2019 at 12:12:29AM +0200, Boris Petkov wrote:
> On September 5, 2019 12:06:54 AM GMT+02:00, Boris Ostrovsky <boris.ostrovsky@...cle.com> wrote:
> >Why do we need to taint kernel here? We are not making any changes.
> 
> Because this is not a normal operation we want users to do. This is only for testing microcode quicker.
> 
> >This won't allow people to load from new microcode blob which I thought
> >was one of the objectives behind this new feature.
> 
> You load a new blob the usual way: echo 1 > ...
> 
> This is the "unusual" way where you reload an already loaded revision only.

But echo 2 > reload would allow reading a microcode file from 
/lib/firmware/intel-ucode/ even if the revision hasn't changed right?

#echo 1 > reload wouldn't load if the revision on disk is same as what's loaded,
and we want to permit that with the echo 2 option.