From patchwork Mon Jul 10 19:48:55 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 13307547 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 53782C001B0 for ; Mon, 10 Jul 2023 19:50:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229741AbjGJTur (ORCPT ); Mon, 10 Jul 2023 15:50:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51456 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229659AbjGJTuq (ORCPT ); Mon, 10 Jul 2023 15:50:46 -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 94827198 for ; Mon, 10 Jul 2023 12:49:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689018553; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=V8XTPlLt8h9osvtrHWj/nnm4IOfNvjA5a3kfsjNIri8=; b=Jby9KlBji81KmIWc8EF2sc2Paw6h71RZpB6d6C9+5n+grglaAVSLlwna1MpVlWjeml1ffM mINKJQTCAxICVuhfU1Yj9dLKnj+5DCTWPlSrhMGdWM6MbTruLOBGhb+x9UvToT1j7n9EL5 5LzewMpn8r4pYi716zLnVquI9eoLBKk= 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-449-cOWTCb-nMjCc6MG-0HCf_A-1; Mon, 10 Jul 2023 15:49:09 -0400 X-MC-Unique: cOWTCb-nMjCc6MG-0HCf_A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1A10F104458F; Mon, 10 Jul 2023 19:49:09 +0000 (UTC) Received: from llong.com (unknown [10.22.18.171]) by smtp.corp.redhat.com (Postfix) with ESMTP id 38CC4111E3E6; Mon, 10 Jul 2023 19:49:08 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Josh Poimboeuf , Pawan Gupta , Jacob Pan , Len Brown , Jonathan Corbet , "Rafael J . Wysocki" Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org, linux-pm@vger.kernel.org, Robin Jarry , Joe Mario , Randy Dunlap , Waiman Long Subject: [PATCH v5 2/4] x86/idle: Disable IBRS when cpu is offline Date: Mon, 10 Jul 2023 15:48:55 -0400 Message-Id: <20230710194857.2898284-3-longman@redhat.com> In-Reply-To: <20230710194857.2898284-1-longman@redhat.com> References: <20230710194857.2898284-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Commit bf5835bcdb96 ("intel_idle: Disable IBRS during long idle") disables IBRS when the CPU enters long idle. However, when a CPU becomes offline, the IBRS bit is still set when X86_FEATURE_KERNEL_IBRS is enabled. That will impact the performance of a sibling CPU. Mitigate this performance impact by clearing all the mitigation bits in SPEC_CTRL MSR when offline. When the CPU is online again, it will be re-initialized and so restoring the SPEC_CTRL value isn't needed. Add a comment to say that native_play_dead() is a __noreturn function, but it can't be marked as such to avoid confusion about the missing MSR restoration code. Signed-off-by: Waiman Long Acked-by: Rafael J. Wysocki --- arch/x86/kernel/smpboot.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index e1aa2cd7734b..68e2e044ab8b 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -87,6 +87,7 @@ #include #include #include +#include /* representing HT siblings of each logical CPU */ DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_sibling_map); @@ -1743,8 +1744,15 @@ void __noreturn hlt_play_dead(void) native_halt(); } +/* + * native_play_dead() is essentially a __noreturn function, but it can't + * be marked as such as the compiler may complain about it. + */ void native_play_dead(void) { + if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS)) + __update_spec_ctrl(0); + play_dead_common(); tboot_shutdown(TB_SHUTDOWN_WFS);