From nobody Mon Sep 15 22:56:49 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2790C6379F for ; Mon, 9 Jan 2023 16:08:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237315AbjAIQI3 (ORCPT ); Mon, 9 Jan 2023 11:08:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237074AbjAIQIP (ORCPT ); Mon, 9 Jan 2023 11:08:15 -0500 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 353983B90C; Mon, 9 Jan 2023 08:08:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: MIME-Version:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type: Content-ID:Content-Description:In-Reply-To:References; bh=IWQp+dbz3tPD0BbW9vxQ/2vTC08Sy+DyjJEG4zi6onc=; b=bWZV7XQCDnsvNcJYDEt+yN0Gpr qAsThBNTT2qcDVAocJUuYke/IzZp9PsXtxRfNEO5cYm3ViZ3wfbe4Kjo0pXcWoeVCtjpd0r4RR3G5 7iMANrOV6Ah2wfvpD88fvkwv9mgkguihyWZW/MkY37P1N1rbm2kcBLhz2cUZTPqOuB/CKN9DFsWHj zSCok+TUcDATD4ITzDShlsIju/ouElkn8HRhzdJaOH27OGtHC6KxPxEJ8SwnKye/zT+04L3o89tpB HUL529/FVigqt+4e6L7FjA9Jx0ZkrUnLxQ2owRWz6h9E3ghQnACcw5xKvraP3Y2YlUUs6WUIYBFjU /an4UiYg==; Received: from [2601:1c2:d80:3110::a2e7] (helo=bombadil.infradead.org) by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1pEuh0-002UBK-NY; Mon, 09 Jan 2023 16:08:10 +0000 From: Randy Dunlap To: linux-kernel@vger.kernel.org Cc: Randy Dunlap , Thomas Gleixner , Borislav Petkov , Ingo Molnar , Dave Hansen , x86@kernel.org, Jonathan Corbet , linux-doc@vger.kernel.org, Ingo Molnar Subject: [PATCH v2] x86/retbleed: add "stuff" mode admin documentation Date: Mon, 9 Jan 2023 08:08:08 -0800 Message-Id: <20230109160808.30740-1-rdunlap@infradead.org> X-Mailer: git-send-email 2.39.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Add admin documentation for "retbleed=3Dstuff", based on commit description and source code. Fixes: d82a0345cf21 ("x86/retbleed: Add call depth tracking mitigation") Signed-off-by: Randy Dunlap Cc: Thomas Gleixner Cc: Borislav Petkov Cc: Ingo Molnar Cc: Dave Hansen Cc: x86@kernel.org Cc: Jonathan Corbet Cc: linux-doc@vger.kernel.org Acked-by: Ingo Molnar --- v2: fix typo "if effect" -> "in effect" (thanks Ingo) Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++ 1 file changed, 8 insertions(+) diff -- a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/a= dmin-guide/kernel-parameters.txt --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5364,6 +5364,14 @@ when STIBP is not available. This is the alternative for systems which do not have STIBP. + 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. unret - Force enable untrained return thunks, only effective on AMD f15h-f17h based systems.