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

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Message-ID: <41cee473-321c-2758-032a-ccf0f01359dc@oracle.com>
Date:   Wed, 4 Sep 2019 18:06:54 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Borislav Petkov <bp@...en8.de>, "Raj, Ashok" <ashok.raj@...el.com>
Cc:     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
Subject: Re: [PATCH] x86/microcode: Add an option to reload microcode even if
 revision is unchanged

On 9/3/19 12:46 PM, Borislav Petkov wrote:
>
>  
> @@ -629,8 +639,12 @@ static ssize_t reload_store(struct device *dev,
>  	if (ret)
>  		return ret;
>  
> -	if (val != 1)
> +	if (val == 2) {
> +		add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);

Why do we need to taint kernel here? We are not making any changes.


> +		return microcode_reload_late(apply_microcode_nocheck);
> +	} else if (val != 1) {
>  		return size;
> +	}
>  
>  	tmp_ret = microcode_ops->request_microcode_fw(bsp, &microcode_pdev->dev, true);

This won't allow people to load from new microcode blob which I thought
was one of the objectives behind this new feature.

-boris