From mboxrd@z Thu Jan 1 00:00:00 1970 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 EFF1483A10; Mon, 15 Apr 2024 14:31:17 +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=1713191478; cv=none; b=Lp9A+vufQwa/Jm0Ik00FfhaoBHgaAq+8v6FkaCJtHENeLdO9rKJ4NpT3deUPE0kXPZC8faWdoRv4izsV8Qvi4JMljeKJ4VHzAXUSyEQEIqqvlac8SM8you4431Qok5MAPiCcU7jNdOEmb9Eqa0Rp9/h7azz0JBAS/VoVV2c64Hg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713191478; c=relaxed/simple; bh=KOMQ4WQ7UflswVSYQCOzT6pn6ft4jpuCgrt4+5QLrBM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gO3+i0KXRr+J2drssvPEBfy/xW+D5Lhs7XOHJeD3By+e9A0HgR5x5BIuKuJr7Pww+/lxRlmQ7eMIMeqJdBSrcHa4oQbiiAzow5wBxTdW0duX92EYfFoFbwztyZffuiQJqME8SGzbJGAMZ+gSsqQQEVc7ejycPCOWeHWBoRvPE1k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=QxVozywM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="QxVozywM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30A9EC2BD10; Mon, 15 Apr 2024 14:31:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1713191477; bh=KOMQ4WQ7UflswVSYQCOzT6pn6ft4jpuCgrt4+5QLrBM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QxVozywMeA0LzQlW6JR4dNZosEjjNLYsSZYhI1YQzPiKYZj/PnDDzhmBDZbWneR9L IA5PFYlxfPKhwrB1qM6xUXsbnrXHdS84QKelTsZ+BjG+UqPeFRnvgMekDK/5ysr/dg Ou6W6rzWvmA/eCdUl+6+OsprdWpH9th1JAMhBf4s= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Josh Poimboeuf , Ingo Molnar , Linus Torvalds , Sean Christopherson Subject: [PATCH 6.8 155/172] x86/bugs: Fix BHI handling of RRSBA Date: Mon, 15 Apr 2024 16:20:54 +0200 Message-ID: <20240415142005.069653811@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240415141959.976094777@linuxfoundation.org> References: <20240415141959.976094777@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josh Poimboeuf commit 1cea8a280dfd1016148a3820676f2f03e3f5b898 upstream. The ARCH_CAP_RRSBA check isn't correct: RRSBA may have already been disabled by the Spectre v2 mitigation (or can otherwise be disabled by the BHI mitigation itself if needed). In that case retpolines are fine. Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob") Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Linus Torvalds Cc: Sean Christopherson Link: https://lore.kernel.org/r/6f56f13da34a0834b69163467449be7f58f253dc.1712813475.git.jpoimboe@kernel.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/bugs.c | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1537,20 +1537,25 @@ static enum spectre_v2_mitigation __init return SPECTRE_V2_RETPOLINE; } +static bool __ro_after_init rrsba_disabled; + /* Disable in-kernel use of non-RSB RET predictors */ static void __init spec_ctrl_disable_kernel_rrsba(void) { - u64 x86_arch_cap_msr; + if (rrsba_disabled) + return; - if (!boot_cpu_has(X86_FEATURE_RRSBA_CTRL)) + if (!(x86_arch_cap_msr & ARCH_CAP_RRSBA)) { + rrsba_disabled = true; return; + } - x86_arch_cap_msr = x86_read_arch_cap_msr(); + if (!boot_cpu_has(X86_FEATURE_RRSBA_CTRL)) + return; - if (x86_arch_cap_msr & ARCH_CAP_RRSBA) { - x86_spec_ctrl_base |= SPEC_CTRL_RRSBA_DIS_S; - update_spec_ctrl(x86_spec_ctrl_base); - } + x86_spec_ctrl_base |= SPEC_CTRL_RRSBA_DIS_S; + update_spec_ctrl(x86_spec_ctrl_base); + rrsba_disabled = true; } static void __init spectre_v2_determine_rsb_fill_type_at_vmexit(enum spectre_v2_mitigation mode) @@ -1651,9 +1656,11 @@ static void __init bhi_select_mitigation return; /* Retpoline mitigates against BHI unless the CPU has RRSBA behavior */ - if (cpu_feature_enabled(X86_FEATURE_RETPOLINE) && - !(x86_read_arch_cap_msr() & ARCH_CAP_RRSBA)) - return; + if (cpu_feature_enabled(X86_FEATURE_RETPOLINE)) { + spec_ctrl_disable_kernel_rrsba(); + if (rrsba_disabled) + return; + } if (spec_ctrl_bhi_dis()) return; @@ -2808,8 +2815,7 @@ static const char *spectre_bhi_state(voi return "; BHI: BHI_DIS_S"; else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP)) return "; BHI: SW loop, KVM: SW loop"; - else if (boot_cpu_has(X86_FEATURE_RETPOLINE) && - !(x86_arch_cap_msr & ARCH_CAP_RRSBA)) + else if (boot_cpu_has(X86_FEATURE_RETPOLINE) && rrsba_disabled) return "; BHI: Retpoline"; else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT)) return "; BHI: Syscall hardening, KVM: SW loop";