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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,URIBL_BLOCKED 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 BAD4EECDFB0 for ; Fri, 13 Jul 2018 19:00:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B7ED208A4 for ; Fri, 13 Jul 2018 19:00:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Dfp0yIJa" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4B7ED208A4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731868AbeGMTQA (ORCPT ); Fri, 13 Jul 2018 15:16:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:40396 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731261AbeGMTQA (ORCPT ); Fri, 13 Jul 2018 15:16:00 -0400 Received: from mail-wr1-f44.google.com (mail-wr1-f44.google.com [209.85.221.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 68E6A208E2 for ; Fri, 13 Jul 2018 19:00:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1531508406; bh=wCj4E/GRmkGhDP2XocWWGrkQj7s61gwkL4GRxxfn1Dc=; h=In-Reply-To:References:From:Date:Subject:To:Cc:From; b=Dfp0yIJaVS+rbrY8+1k/vFGBki5dYddRmoT88nEqSVw6bMmGJAQlxHE7Fg1c+isVA YIkDzpfi0hIMSY1k1Dy9kTJuaBWxsgL6BQvgCi2v5ZFJWJawgrR00T0XHCR2iQjTpV eeZcKfKl9t5xUylhXpSORdVYAeBpX4WtV6E6wAuE= Received: by mail-wr1-f44.google.com with SMTP id b15-v6so26105781wrv.10 for ; Fri, 13 Jul 2018 12:00:06 -0700 (PDT) X-Gm-Message-State: AOUpUlG0CI3/O/W/RzD100phIu+r9LrNc4Izpb8KRE6Y5CycpTgBUXd2 55t7fT/TXnbnKz2j834DJvWocHsC+W8rFyHxYy0bHA== X-Google-Smtp-Source: AAOMgpfWFqGYZwlC17CfBB5LJncGJiknZtsAT+glCSdzMDUscy2omCNMrp0yLfIVaTDgTx5bo9HLoi3VL1/qRG9rxqE= X-Received: by 2002:adf:e0cc:: with SMTP id e12-v6mr5628140wri.199.1531508404809; Fri, 13 Jul 2018 12:00:04 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a1c:d548:0:0:0:0:0 with HTTP; Fri, 13 Jul 2018 11:59:44 -0700 (PDT) In-Reply-To: <1531308586-29340-39-git-send-email-joro@8bytes.org> References: <1531308586-29340-1-git-send-email-joro@8bytes.org> <1531308586-29340-39-git-send-email-joro@8bytes.org> From: Andy Lutomirski Date: Fri, 13 Jul 2018 11:59:44 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 38/39] x86/mm/pti: Add Warning when booting on a PCID capable CPU To: Joerg Roedel , Borislav Petkov Cc: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , X86 ML , LKML , Linux-MM , Linus Torvalds , Andy Lutomirski , Dave Hansen , Josh Poimboeuf , Juergen Gross , Peter Zijlstra , Jiri Kosina , Boris Ostrovsky , Brian Gerst , David Laight , Denys Vlasenko , Eduardo Valentin , Greg KH , Will Deacon , "Liguori, Anthony" , Daniel Gruss , Hugh Dickins , Kees Cook , Andrea Arcangeli , Waiman Long , Pavel Machek , "David H . Gutteridge" , Joerg Roedel Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 11, 2018 at 4:29 AM, Joerg Roedel wrote: > From: Joerg Roedel > > Warn the user in case the performance can be significantly > improved by switching to a 64-bit kernel. ... > +#ifdef CONFIG_X86_32 > + if (boot_cpu_has(X86_FEATURE_PCID)) { I'm a bit confused. Wouldn't the setup_clear_cpu_cap() call in early_identify_cpu() prevent this from working? Boris, do we have a straightforward way to ask "does the CPU advertise this feature in CPUID regardless of whether we have it enabled right now"? --Andy