From mboxrd@z Thu Jan 1 00:00:00 1970 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 4972AC4332F for ; Mon, 7 Nov 2022 21:19:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232909AbiKGVS6 (ORCPT ); Mon, 7 Nov 2022 16:18:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41144 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233619AbiKGVSP (ORCPT ); Mon, 7 Nov 2022 16:18:15 -0500 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2909326C7 for ; Mon, 7 Nov 2022 13:15:18 -0800 (PST) Received: from zn.tnic (p200300ea9733e764329c23fffea6a903.dip0.t-ipconnect.de [IPv6:2003:ea:9733:e764:329c:23ff:fea6:a903]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 509E71EC059D; Mon, 7 Nov 2022 22:15:17 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1667855717; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type: content-transfer-encoding:content-transfer-encoding:in-reply-to: references; bh=rbOTxD9ZKYlilVo5kI9gEidbFcfzuiyGtj4TcpECXu8=; b=DDfYNpFeTRMchdM0zB46lZpL48UYZdZzPzivVPw4P3pVwGaS3U8nPQgcgud1I4aocQ9CVV bAh2I6THf6v173aVuwdcmsXeaMGL5e5d9Qum20MRkjY+D0ba2ogrT9DGkSZm+gork34ZpF iszaL1Q3Tbr4CPSeLcOVoXoi3tkL1KU= From: Borislav Petkov To: X86 ML Cc: LKML Subject: [PATCH] x86/cpu: Start documenting what the X86_FEATURE_ flag testing macros do Date: Mon, 7 Nov 2022 22:15:05 +0100 Message-Id: <20221107211505.8572-1-bp@alien8.de> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Borislav Petkov ... and how and when they should be used. This keeps popping up everytime people start poking at the CPU features testing machinery - which has admittedly grown some warts and would need cleaning up - or when they are wondering what function/macro to use. Start documenting it first. Proper cleanup will follow once all the functionality has been agreed upon. No functional changes. Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220718141123.136106-3-mlevitsk@redhat.com --- arch/x86/include/asm/cpufeature.h | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 1a85e1fb0922..47ff025e7387 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -131,12 +131,13 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; (unsigned long __percpu *)&cpu_info.x86_capability)) /* - * This macro is for detection of features which need kernel - * infrastructure to be used. It may *not* directly test the CPU - * itself. Use the cpu_has() family if you want true runtime - * testing of CPU features, like in hypervisor code where you are - * supporting a possible guest feature where host support for it - * is not relevant. + * This is the preferred macro to use when testing X86_FEATURE_ bits + * support without the need to test on a particular CPU but rather + * system-wide. It takes into account build-time disabled feature + * support too. All those macros mirror the kernel's idea of enabled + * CPU features and not necessarily what real, hardware CPUID bits are + * set or clear. For that use tools/arch/x86/kcpuid/ and/or potentially + * extend if it's feature list is lacking. */ #define cpu_feature_enabled(bit) \ (__builtin_constant_p(bit) && DISABLED_MASK_BIT_SET(bit) ? 0 : static_cpu_has(bit)) @@ -145,9 +146,15 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; #define set_cpu_cap(c, bit) set_bit(bit, (unsigned long *)((c)->x86_capability)) -extern void setup_clear_cpu_cap(unsigned int bit); extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit); +/* + * The setup_* prefixed variants enable/disable feature bits on all + * CPUs in the system and are used to replicate those settings before + * apply_forced_caps() has synthesized enabled and disabled bits across + * every CPU. + */ +extern void setup_clear_cpu_cap(unsigned int bit); #define setup_force_cpu_cap(bit) do { \ set_cpu_cap(&boot_cpu_data, bit); \ set_bit(bit, (unsigned long *)cpu_caps_set); \ -- 2.35.1