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 X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 778FBC433F5 for ; Thu, 9 Sep 2021 22:08:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 568E56115A for ; Thu, 9 Sep 2021 22:08:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343804AbhIIWJ4 (ORCPT ); Thu, 9 Sep 2021 18:09:56 -0400 Received: from terminus.zytor.com ([198.137.202.136]:47923 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231819AbhIIWJy (ORCPT ); Thu, 9 Sep 2021 18:09:54 -0400 Received: from tazenda.hos.anvin.org ([IPv6:2601:646:8600:3c70:7285:c2ff:fefb:fd4]) (authenticated bits=0) by mail.zytor.com (8.16.1/8.15.2) with ESMTPSA id 189M8Rx1240627 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Thu, 9 Sep 2021 15:08:34 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 189M8Rx1240627 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2021083001; t=1631225314; bh=z6l5KSYd2UWZHXazF9BmrbSsVpVuYtysUQylbL6UGpg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YCPqxJ2Hcn1AAXkLmlRJUTLG3Gx/wwnepYIVidE9ChSF8Ye9t4DuDx64BR0fVZ+uq DX4cLDcx3HNUp6UX9kwvkIzO2JbjLHC7oILQ+DQ4GBGdHqumpv3etF1EyNPOeoEc58 NEg5HIcV7GKMIL4syuyLfxZO8Yinq8h4Af1TDKKgSTZKmieGniH0mcMDTnyKGZoJuQ gohRYjuOBIcV3FqyOPbdRKAws5fnxodsWqYlnbZ4dZ6TZSkzn5KHJFyDpUu+EgNnjz 5wOrqCjibI8ztqrfb8TIWkjkqtxJAS0O/kUPxOnTG6CwmOUx6D8CF14FMPc/3W8TVi NJmEx9BB32mLQ== From: "H. Peter Anvin (Intel)" To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski Cc: Linux Kernel Mailing List , x86@kernel.org, "H. Peter Anvin (Intel)" Subject: [PATCH v2 0/2] x86/asm: avoid register pressure from static_cpu_has() Date: Thu, 9 Sep 2021 15:08:16 -0700 Message-Id: <20210909220818.417312-1-hpa@zytor.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210908171716.3340120-1-hpa@zytor.com> References: <20210908171716.3340120-1-hpa@zytor.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org gcc will sometimes manifest the address of boot_cpu_data in a register as part of constant propagation. When multiple static_cpu_has() are used this may foul the mainline code with a register load which will only be used on the fallback path, which is unused after initialization. Explicitly force gcc to use immediate (rip-relative) addressing for the fallback path, thus removing any possible register use from static_cpu_has(). However, currently there is no convenient way to make gcc generate a %rip-relative immediate reference without splitting code into i386 and x86-64 versions, so add a new macro to for this purpose. Changes in v2: -------------- * Add new macro to * *Actually* generate the %rip-relative addressing mode.