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 012CCEB64DA for ; Thu, 22 Jun 2023 12:32:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230446AbjFVMcy (ORCPT ); Thu, 22 Jun 2023 08:32:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231293AbjFVMcx (ORCPT ); Thu, 22 Jun 2023 08:32:53 -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 ED2BCE75 for ; Thu, 22 Jun 2023 05:32:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1687437123; 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=XHz9E7zZxsLUl3CoUFODhh8sjTY5W8aaMW7xXwi0QZ4=; b=ZbkdFIDSVP1DCZ0bYdUnRQX7SSdzWNzEZnQQCcvrZ8DFXOa4EQ4kmPgWn1AIZg72muVmJk 12T0x7oJpe2KiQaKfktXzCLzu8M+85L6N1QWSSYVb9gP14IPD6FmfB0XBS6Q/4RAT7P4TI SzEukcxhdZ87GWBjQGAhFaqRiyYgBys= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-507-4Ekn8PXCOCe4mV43ZjKflQ-1; Thu, 22 Jun 2023 08:31:58 -0400 X-MC-Unique: 4Ekn8PXCOCe4mV43ZjKflQ-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 18D4E881B25; Thu, 22 Jun 2023 12:31:58 +0000 (UTC) Received: from [10.22.17.29] (unknown [10.22.17.29]) by smtp.corp.redhat.com (Postfix) with ESMTP id 722CA200A3AD; Thu, 22 Jun 2023 12:31:57 +0000 (UTC) Message-ID: <7b8a5195-83c4-5433-6261-24e0941a1cab@redhat.com> Date: Thu, 22 Jun 2023 08:31:57 -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: Josh Poimboeuf Cc: Peter Zijlstra , 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> From: Waiman Long In-Reply-To: <20230622054633.ulrurzzvzjijvdhn@treble> 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-pm@vger.kernel.org On 6/22/23 01:46, 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? It is not a bug per se. It is mainly to make the per cpu variable more up to date. > >> Signed-off-by: Waiman Long >> --- >> drivers/idle/intel_idle.c | 8 ++++++-- >> 1 file changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c >> index aa2d19db2b1d..07fa23707b3c 100644 >> --- a/drivers/idle/intel_idle.c >> +++ b/drivers/idle/intel_idle.c >> @@ -181,13 +181,17 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev, >> u64 spec_ctrl = spec_ctrl_current(); >> int ret; >> >> - if (smt_active) >> + if (smt_active) { >> + __this_cpu_write(x86_spec_ctrl_current, 0); >> native_wrmsrl(MSR_IA32_SPEC_CTRL, 0); >> + } >> >> ret = __intel_idle(dev, drv, index); >> >> - if (smt_active) >> + if (smt_active) { >> native_wrmsrl(MSR_IA32_SPEC_CTRL, spec_ctrl); >> + __this_cpu_write(x86_spec_ctrl_current, spec_ctrl); >> + } > More candidates for update_spec_ctrl()? I don't think we can use update_spec_ctrl() here simply because of the noinstr requirement. See commit 9b461a6faae7 ("cpuidle, intel_idle: Fix CPUIDLE_FLAG_IBRS"). Cheers, Longman