From nobody Wed Dec 17 21:28:09 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 9CE4BC3DA40 for ; Wed, 16 Aug 2023 07:56:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242568AbjHPHze (ORCPT ); Wed, 16 Aug 2023 03:55:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49068 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242614AbjHPHzV (ORCPT ); Wed, 16 Aug 2023 03:55:21 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D98FF26A9; Wed, 16 Aug 2023 00:55:17 -0700 (PDT) Date: Wed, 16 Aug 2023 07:55:14 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1692172515; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NgvPMkdo6adZocli65oddA0uD+22Gh9QHc+5yviNzU8=; b=eg21/HzeCKNBYp4FLRNsvFT3blHgJnJJyVBgLJLu6ymw2W0iv988Ngds1ggcIEKDzVySmp G7HituYoSpExwjpUQN+IpSmgad9bGuhFqm26YrblbLubg2MHt0rOAyXC6u5qcb1UEGioDx DuwJroB1cNQQg64q1YAT+4JvlfmN5y9bkKMTf0SJKP2fl4lf4g5qj+uDVGpLNJ24R9Bi63 gGjOAHulUzGGwg3/8dnBJLrnpbsc6f2taf0FdSglg3Bu+Tdstrw184BOLeHTMHQyvL6XK3 kITbBPGcUllZyKX5nkjFJqGcqms2F9ZyniDQHx12ReAJ/eRYlrwx9r6AsuCsZw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1692172515; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NgvPMkdo6adZocli65oddA0uD+22Gh9QHc+5yviNzU8=; b=FgkULZ+Zrsrsy/9/W+hy5W64K+fwVjxZtxFlRvxT0pWgCzCP1jl02ZZTGoBdrbkH46Qth6 00IAVSonN5qQXWAQ== From: "tip-bot2 for Peter Zijlstra" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] x86/cpu/kvm: Provide UNTRAIN_RET_VM Cc: "Peter Zijlstra (Intel)" , "Borislav Petkov (AMD)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230814121149.109557833@infradead.org> References: <20230814121149.109557833@infradead.org> MIME-Version: 1.0 Message-ID: <169217251477.27769.1201631042444536455.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/urgent branch of tip: Commit-ID: ad63073765fa394665bcb54660cc997f05b704d4 Gitweb: https://git.kernel.org/tip/ad63073765fa394665bcb54660cc997f0= 5b704d4 Author: Peter Zijlstra AuthorDate: Mon, 14 Aug 2023 13:44:35 +02:00 Committer: Borislav Petkov (AMD) CommitterDate: Wed, 16 Aug 2023 09:39:16 +02:00 x86/cpu/kvm: Provide UNTRAIN_RET_VM Similar to how it doesn't make sense to have UNTRAIN_RET have two untrain calls, it also doesn't make sense for VMEXIT to have an extra IBPB call. This cures VMEXIT doing potentially unret+IBPB or double IBPB. Also, the (SEV) VMEXIT case seems to have been overlooked. Redefine the meaning of the synthetic IBPB flags to: - ENTRY_IBPB -- issue IBPB on entry (was: entry + VMEXIT) - IBPB_ON_VMEXIT -- issue IBPB on VMEXIT And have 'retbleed=3Dibpb' set *BOTH* feature flags to ensure it retains the previous behaviour and issues IBPB on entry+VMEXIT. The new 'srso=3Dibpb_vmexit' option only sets IBPB_ON_VMEXIT. Create UNTRAIN_RET_VM specifically for the VMEXIT case, and have that check IBPB_ON_VMEXIT. All this avoids having the VMEXIT case having to check both ENTRY_IBPB and IBPB_ON_VMEXIT and simplifies the alternatives. Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20230814121149.109557833@infradead.org --- arch/x86/include/asm/nospec-branch.h | 11 +++++++++++ arch/x86/kernel/cpu/bugs.c | 1 + arch/x86/kvm/svm/vmenter.S | 7 ++----- 3 files changed, 14 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/no= spec-branch.h index 5285c8e..c55cc24 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -299,6 +299,17 @@ #endif .endm =20 +.macro UNTRAIN_RET_VM +#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ + defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) + VALIDATE_UNRET_END + ALTERNATIVE_3 "", \ + CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ + "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT, \ + __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH +#endif +.endm + .macro UNTRAIN_RET_FROM_CALL #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ defined(CONFIG_CALL_DEPTH_TRACKING) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 6f3e195..9026e3f 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1054,6 +1054,7 @@ do_cmd_auto: =20 case RETBLEED_MITIGATION_IBPB: setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB); + setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT); mitigate_smt =3D true; break; =20 diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S index 265452f..ef2ebab 100644 --- a/arch/x86/kvm/svm/vmenter.S +++ b/arch/x86/kvm/svm/vmenter.S @@ -222,10 +222,7 @@ SYM_FUNC_START(__svm_vcpu_run) * because interrupt handlers won't sanitize 'ret' if the return is * from the kernel. */ - UNTRAIN_RET - - /* SRSO */ - ALTERNATIVE "", "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT + UNTRAIN_RET_VM =20 /* * Clear all general purpose registers except RSP and RAX to prevent @@ -362,7 +359,7 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run) * because interrupt handlers won't sanitize RET if the return is * from the kernel. */ - UNTRAIN_RET + UNTRAIN_RET_VM =20 /* "Pop" @spec_ctrl_intercepted. */ pop %_ASM_BX