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 34334EB64D8 for ; Thu, 22 Jun 2023 12:35:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231393AbjFVMfy (ORCPT ); Thu, 22 Jun 2023 08:35:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43026 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229585AbjFVMfv (ORCPT ); Thu, 22 Jun 2023 08:35:51 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A5045B4 for ; Thu, 22 Jun 2023 05:35:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1687437307; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=r5InBmmxDXVDwgBLrdcfId/Pttqu0CWzwtLP5BOUwdA=; b=LqrnpCuZKcLDtPcbo5TDYw9mmW3VoLxl2zHrPDSgxmSE/eO6D1yLUH9acFtVZMxRjproGr uwxPOtw9UwseaPK3GKM069cyX/hzy782ip5Cc7foVUrD+LVULaKMhmF6lIz7NckaFtYUDz ssbcYZAg0j8T30eoMiug9YUf+F7xTMA= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-399-wjIUS_jCN0yMp1UHsQTgAw-1; Thu, 22 Jun 2023 08:35:04 -0400 X-MC-Unique: wjIUS_jCN0yMp1UHsQTgAw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 42C8C3C1392C; Thu, 22 Jun 2023 12:35:00 +0000 (UTC) Received: from [10.22.17.29] (unknown [10.22.17.29]) by smtp.corp.redhat.com (Postfix) with ESMTP id 96A08200A3AD; Thu, 22 Jun 2023 12:34:59 +0000 (UTC) Message-ID: <87c6e059-d010-a8aa-8e63-7b09d82be863@redhat.com> Date: Thu, 22 Jun 2023 08:34:59 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [PATCH v3 2/3] intel_idle: Sync up the SPEC_CTRL MSR value to x86_spec_ctrl_current Content-Language: en-US To: Peter Zijlstra , Josh Poimboeuf Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Pawan Gupta , Jacob Pan , Len Brown , linux-kernel@vger.kernel.org, x86@kernel.org, linux-pm@vger.kernel.org, Robin Jarry , Joe Mario References: <20230622003603.1188364-1-longman@redhat.com> <20230622003603.1188364-3-longman@redhat.com> <20230622054633.ulrurzzvzjijvdhn@treble> <20230622094051.GF4253@hirez.programming.kicks-ass.net> From: Waiman Long In-Reply-To: <20230622094051.GF4253@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/22/23 05:40, Peter Zijlstra wrote: > On Wed, Jun 21, 2023 at 10:46:33PM -0700, Josh Poimboeuf wrote: >> On Wed, Jun 21, 2023 at 08:36:02PM -0400, Waiman Long wrote: >>> When intel_idle_ibrs() is called, it modifies the SPEC_CTRL MSR to >>> 0 in order disable IBRS. However, the new MSR value isn't reflected >>> in x86_spec_ctrl_current which is at odd with the other code that >>> keep track of its state in that percpu variable. Fix that by updating >>> x86_spec_ctrl_current percpu value to always match the content of the >>> SPEC_CTRL MSR. >> Is this fixing an actual bug or is there some other reason for doing >> this? > No actual bug, he did this for his debugfs file -- which is no longer > part of the series. With that on, you can observe the > x86_spec_ctrl_current value while idle. Right. That is the main reason as I want the SPEC_CTRL MSRs value to be observable by some external mean:-) Regards, Longman