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 D7C921DFF4; Mon, 1 Apr 2024 16:57:23 +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=1711990643; cv=none; b=T+sF5YzpotLG01x5FkdiEZyseQ9Aag3PrnznDigr2glH4+Ph/gFenmmDHqGALRtcQNDE35J7F/2qg212gMuvmntxX2gUWgW08smshkaP9V88Wljr447IJ4yd+xBo1EuV+Izo35Z5x97+fmHjnAHOJwbYaFBBRLuhpgVwsZzPgSs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711990643; c=relaxed/simple; bh=BJ9s33zGqxDHmqIRuAsB8dH8hPSitdVPVq4VRgpqkMs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EHVPuuGQSd7JtB6tFZLuDAnWF+zme1aAv3ho58V7xprwyJqChWbAGk4Wfp/dI+KEvgafUYZ1zHzAFkINTMvU/Ya3vRjb/suiytcg8K2FgeemX+1yYFQyyFoWy5rR/DOJiIK5no7cObVA5HIDVaDvgNaikRofkJbWnriEVnVI7ds= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=KgvUu3+f; 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="KgvUu3+f" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5C057C433F1; Mon, 1 Apr 2024 16:57:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1711990643; bh=BJ9s33zGqxDHmqIRuAsB8dH8hPSitdVPVq4VRgpqkMs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KgvUu3+fcg6nOJWh9D4OwmwcKj5AvH67f46ca8rn59Fk6Ic+O0t933aA47g0lWd/D AvVewST5ZIofTArFJDus7T6t/RBltg185ka1xO3Owq/ZWbaGbX03/xetUVnMwpdMUo lTas2oVmdo0owCtzgymR9Izv7Matur0QjorDdXuk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jim Mattson , Sean Christopherson Subject: [PATCH 6.1 005/272] KVM: x86: Use a switch statement and macros in __feature_translate() Date: Mon, 1 Apr 2024 17:43:15 +0200 Message-ID: <20240401152530.438741679@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240401152530.237785232@linuxfoundation.org> References: <20240401152530.237785232@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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jim Mattson commit 80c883db87d9ffe2d685e91ba07a087b1c246c78 upstream. Use a switch statement with macro-generated case statements to handle translating feature flags in order to reduce the probability of runtime errors due to copy+paste goofs, to make compile-time errors easier to debug, and to make the code more readable. E.g. the compiler won't directly generate an error for duplicate if statements if (x86_feature == X86_FEATURE_SGX1) return KVM_X86_FEATURE_SGX1; else if (x86_feature == X86_FEATURE_SGX2) return KVM_X86_FEATURE_SGX1; and so instead reverse_cpuid_check() will fail due to the untranslated entry pointing at a Linux-defined leaf, which provides practically no hint as to what is broken arch/x86/kvm/reverse_cpuid.h:108:2: error: call to __compiletime_assert_450 declared with 'error' attribute: BUILD_BUG_ON failed: x86_leaf == CPUID_LNX_4 BUILD_BUG_ON(x86_leaf == CPUID_LNX_4); ^ whereas duplicate case statements very explicitly point at the offending code: arch/x86/kvm/reverse_cpuid.h:125:2: error: duplicate case value '361' KVM_X86_TRANSLATE_FEATURE(SGX2); ^ arch/x86/kvm/reverse_cpuid.h:124:2: error: duplicate case value '360' KVM_X86_TRANSLATE_FEATURE(SGX1); ^ And without macros, the opposite type of copy+paste goof doesn't generate any error at compile-time, e.g. this yields no complaints: case X86_FEATURE_SGX1: return KVM_X86_FEATURE_SGX1; case X86_FEATURE_SGX2: return KVM_X86_FEATURE_SGX1; Note, __feature_translate() is forcibly inlined and the feature is known at compile-time, so the code generation between an if-elif sequence and a switch statement should be identical. Signed-off-by: Jim Mattson Link: https://lore.kernel.org/r/20231024001636.890236-2-jmattson@google.com [sean: use a macro, rewrite changelog] Signed-off-by: Sean Christopherson Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/reverse_cpuid.h | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) --- a/arch/x86/kvm/reverse_cpuid.h +++ b/arch/x86/kvm/reverse_cpuid.h @@ -97,14 +97,16 @@ static __always_inline void reverse_cpui */ static __always_inline u32 __feature_translate(int x86_feature) { - if (x86_feature == X86_FEATURE_SGX1) - return KVM_X86_FEATURE_SGX1; - else if (x86_feature == X86_FEATURE_SGX2) - return KVM_X86_FEATURE_SGX2; - else if (x86_feature == X86_FEATURE_RRSBA_CTRL) - return KVM_X86_FEATURE_RRSBA_CTRL; +#define KVM_X86_TRANSLATE_FEATURE(f) \ + case X86_FEATURE_##f: return KVM_X86_FEATURE_##f - return x86_feature; + switch (x86_feature) { + KVM_X86_TRANSLATE_FEATURE(SGX1); + KVM_X86_TRANSLATE_FEATURE(SGX2); + KVM_X86_TRANSLATE_FEATURE(RRSBA_CTRL); + default: + return x86_feature; + } } static __always_inline u32 __feature_leaf(int x86_feature)