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=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 4E99BC43441 for ; Thu, 22 Nov 2018 06:58:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0A3C220878 for ; Thu, 22 Nov 2018 06:58:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="h6UNB55T" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0A3C220878 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.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 S2392325AbeKVRg4 (ORCPT ); Thu, 22 Nov 2018 12:36:56 -0500 Received: from mail.kernel.org ([198.145.29.99]:49166 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392311AbeKVRg4 (ORCPT ); Thu, 22 Nov 2018 12:36:56 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EBE2F20865; Thu, 22 Nov 2018 06:58:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1542869932; bh=s19qSokm/XU2WAphuGr6P8xDNduky4UTmSCxlcuH9P0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=h6UNB55TiSR6v2s7fS8hC0/5ufJK6yd5GmnFsGu4xGacCMhXIgEqzTTtpw4sM7jK1 3F77QiL9KJ0T0BDJmtr0dLbDwCoNkb3cj/9cD/hhlBmuboE8gY8Z1fBb7X6Fdco6Bm t57gZJvixCe40Km8KZ8U36Z6zzaVpMfaSotsOCcg= Date: Thu, 22 Nov 2018 07:58:50 +0100 From: Greg KH To: Jiri Kosina Cc: Tim Chen , Thomas Gleixner , Linus Torvalds , Tom Lendacky , Ingo Molnar , Peter Zijlstra , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Andi Kleen , Dave Hansen , Casey Schaufler , Asit Mallick , Arjan van de Ven , Jon Masters , Waiman Long , Dave Stewart , linux-kernel@vger.kernel.org, x86@kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] x86/speculation: Revert turning on STIBP all the time Message-ID: <20181122065850.GA11963@kroah.com> References: <0693f05ac4b041ee2f988dfec31ebc81f4f28f17.1542830344.git.tim.c.chen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 21, 2018 at 09:51:19PM +0100, Jiri Kosina wrote: > On Wed, 21 Nov 2018, Tim Chen wrote: > > > Commit 53c613fe "x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation" > > turns on STIBP all the time. > > > > This causes large performance regression in many workloads. > > > > One case is perlbench in the SpecInt Rate 2006 test suite which shows a > > 21% reduction in throughput. > > There're also other reports of drop in performance on Python and PHP benchmarks: > > https://www.phoronix.com/scan.php?page=article&item=linux-420-bisect&num=2 > > > > STIBP on all the time should not be the default option. > > > > Turn off STIBP all the time for now till STIBP can be applied on > > a per task basis. > > > > Signed-off-by: Tim Chen > > --- > > arch/x86/kernel/cpu/bugs.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c > > index c37e66e..21a8f39 100644 > > --- a/arch/x86/kernel/cpu/bugs.c > > +++ b/arch/x86/kernel/cpu/bugs.c > > @@ -332,7 +332,7 @@ static bool stibp_needed(void) > > if (!boot_cpu_has(X86_FEATURE_STIBP)) > > return false; > > > > - return true; > > + return false; > > } > > For -stable, which actually makes it to production, I already asked Greg > to drop it. It's in the latest stable -rc releases, and if all goes well, they will be released tomorrow. thanks, greg k-h