linux-kernel - Re: [PATCH v2] x86/bugs: Enable STIBP for IBPB mitigated RetBleed

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Message-ID: <Yu66YlFzd4VRZq6/@gmail.com>
Date:   Sat, 6 Aug 2022 21:00:50 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Kim Phillips <kim.phillips@....com>
Cc:     bp@...en8.de, x86@...nel.org, peterz@...radead.org, bp@...e.de,
        bpf@...r.kernel.org, jpoimboe@...hat.com,
        andrew.cooper3@...rix.com, linux-kernel@...r.kernel.org,
        thomas.lendacky@....com
Subject: Re: [PATCH v2] x86/bugs: Enable STIBP for IBPB mitigated RetBleed


* Kim Phillips <kim.phillips@....com> wrote:

>  			Speculative Code Execution with Return Instructions)
>  			vulnerability.
>  
> +			AMD-based unret and ibpb mitigations alone do not stop
> +			sibling threads influencing the predictions of other sibling
> +			threads.  For that reason, we use STIBP on processors
> +			that support it, and mitigate SMT on processors that don't.

>  	 * retbleed_select_mitigation(); specifically the STIBP selection is
> -	 * forced for UNRET.
> +	 * forced for UNRET or IBPB.

Nit: could you please capitalize the acronyms & instruction names 
consistently? Human eyesight is case sensitive.

Ie. it should be UNRET and IBPB everywhere.

Thanks,

	Ingo