linux-kernel - Re: [PATCH v2] x86/retbleed: add "stuff" mode admin documentation

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Message-ID: <ceec97e2-2acd-6f15-5675-6b2b143b972f@intel.com>
Date:   Mon, 9 Jan 2023 09:19:09 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v2] x86/retbleed: add "stuff" mode admin documentation

On 1/9/23 08:08, Randy Dunlap wrote:
> +			stuff        - Enables "stuffing" mode mitigation,
> +				       which uses return thunking and call depth
> +				       tracking.  Only in effect if
> +				       CONFIG_CALL_DEPTH_TRACKING is set and
> +				       Spectre V2 mitigation mode is
> +				       "retpoline".
> +				       IBRS is fully secure mitigation but is
> +				       more costly (slower) than stuffing.

The "fully secure" thing makes me cringe a bit.

I'd suggest saying:

	IBRS is a stronger mitigation
	but is more costly than stuffing
	(slower).