From patchwork Thu Nov 21 20:07:18 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Josh Poimboeuf X-Patchwork-Id: 13882326 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 32E6D1C8773; Thu, 21 Nov 2024 20:07:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732219649; cv=none; b=lIzEoeJmcd/8tdtENAx4AceVALlsR5rQEAr7Dpiir7NePJbGo62/h8iybu6DpKj1GtnEQ+Q/CpqsJmo6M6A3yYJiwCWG6trqzrdjNZQNDuV0J2BzuMpRD5KszafY9wMsnDyRAvHSL4dyAtZ6p7P8mfRg7MImtm+Mf5jLneErjtQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732219649; c=relaxed/simple; bh=FpjLLZz26oP/xzxw3OgjixqR9UwwP/ENIIDlp6IfE2I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OrlJM4iVtQKVWSxJxBC/Yu8gO6+/cy9uAITn+McNrdt9SYfE/4LjzIB2aDExzL9sF0o9HGwjim1vSbT1ElZLpC7+2byL6t7VydD6Wz7o6yW7yFdvbCID5hZ8ENpDmp7ADndHLHqxVG993R8wdNExeshM0Xr76F4QEMCn6+Uq3V4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oWVqjtF0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oWVqjtF0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7E14C4CED2; Thu, 21 Nov 2024 20:07:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732219648; bh=FpjLLZz26oP/xzxw3OgjixqR9UwwP/ENIIDlp6IfE2I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oWVqjtF0LfcKXKv7u/4J8p8uobwGevC3aNnvJ6khsYP3RyYI+sEyIuUcl8q7DefWa dtE3WfuMmFMBqwVXDfRIxcM72590qJ1svl4+MW2VFBkPgehE87KI2LXcz/HzgP/SIj EIzzoFe87uQ5dd7gc4LcrZNzW97wwl01jvRvZFFpkwUE5Ltz2TqCZXzkT4c7kSgpCK Yt3XvlgOfFjWxXZ8+uMsN1ZMCeQjHW+U3RZLJrzyAVm+VoG9uyuwkb+OOV6DDT6NO2 0VN/wr3tgrNIq7p22hlcjd+KxVy9tsdNnuW3zitnoVKKGoYaParwxW7V21ASGNhY/7 gQU1WwG5xviGQ== From: Josh Poimboeuf To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, amit@kernel.org, kvm@vger.kernel.org, amit.shah@amd.com, thomas.lendacky@amd.com, bp@alien8.de, tglx@linutronix.de, peterz@infradead.org, pawan.kumar.gupta@linux.intel.com, corbet@lwn.net, mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com, seanjc@google.com, pbonzini@redhat.com, daniel.sneddon@linux.intel.com, kai.huang@intel.com, sandipan.das@amd.com, boris.ostrovsky@oracle.com, Babu.Moger@amd.com, david.kaplan@amd.com, dwmw@amazon.co.uk, andrew.cooper3@citrix.com Subject: [PATCH v2 1/2] x86/bugs: Don't fill RSB on VMEXIT with eIBRS+retpoline Date: Thu, 21 Nov 2024 12:07:18 -0800 Message-ID: <9bd7809697fc6e53c7c52c6c324697b99a894013.1732219175.git.jpoimboe@kernel.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 eIBRS protects against RSB underflow/poisoning attacks. Adding retpoline to the mix doesn't change that. Retpoline has a balanced CALL/RET anyway. So the current full RSB filling on VMEXIT with eIBRS+retpoline is overkill. Disable it (or do the VMEXIT_LITE mitigation if needed). Suggested-by: Pawan Gupta Reviewed-by: Pawan Gupta Reviewed-by: Amit Shah Signed-off-by: Josh Poimboeuf --- arch/x86/kernel/cpu/bugs.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 47a01d4028f6..68bed17f0980 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1605,20 +1605,20 @@ static void __init spectre_v2_determine_rsb_fill_type_at_vmexit(enum spectre_v2_ case SPECTRE_V2_NONE: return; - case SPECTRE_V2_EIBRS_LFENCE: case SPECTRE_V2_EIBRS: + case SPECTRE_V2_EIBRS_LFENCE: + case SPECTRE_V2_EIBRS_RETPOLINE: if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) { - setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT_LITE); pr_info("Spectre v2 / PBRSB-eIBRS: Retire a single CALL on VMEXIT\n"); + setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT_LITE); } return; - case SPECTRE_V2_EIBRS_RETPOLINE: case SPECTRE_V2_RETPOLINE: case SPECTRE_V2_LFENCE: case SPECTRE_V2_IBRS: - setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT); pr_info("Spectre v2 / SpectreRSB : Filling RSB on VMEXIT\n"); + setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT); return; }