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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, 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 E61D9C43141 for ; Thu, 21 Jun 2018 20:07:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 888DF21E5B for ; Thu, 21 Jun 2018 20:07:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="FGVvafUt" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 888DF21E5B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.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 S1754204AbeFUUHA (ORCPT ); Thu, 21 Jun 2018 16:07:00 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:59218 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753906AbeFUUG7 (ORCPT ); Thu, 21 Jun 2018 16:06:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=lXg9TXZPPDt5ZOaHmKgjD55UOPu3lRFzxeUKise8as8=; b=FGVvafUtkp0esef/cyUZOXETz erRTN4Xbqb18+Nb0P8eHwL9GzwMzU0YFXSLpII5Kyl8loW23eVkYudqfOCXfBTwGj/wxzk0Lhi3Sf kB/NOGYBKzzuKPO3ih7moD76iNwHkuYVE66Vp7u6NsMGF0Y4ZsmAV6cgJ6ijYccWp9x3aIZOwc6tA xlRVkb7l4f9Vvn9lS/K4TMeCnXAr9+hjRzrrZTJK/EKm9RJKLxFycWoXF+e4kGzdU7lWHphFti66M qoBzQM6VcMTSjL07bSl1WdjkwRgAsAJ58g47SOPeEjOaGNxrOKtJhj/yPivBmmVlqWH7Re9pUT9lx /+2B4WAYA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fW5r7-0004U4-8O; Thu, 21 Jun 2018 20:06:57 +0000 Received: by worktop (Postfix, from userid 1000) id A87656E093E; Thu, 21 Jun 2018 22:06:54 +0200 (CEST) Date: Thu, 21 Jun 2018 22:06:54 +0200 From: Peter Zijlstra To: Dave Hansen Cc: Fenghua Yu , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Ashok Raj , Rafael Wysocki , Tony Luck , Alan Cox , Ravi V Shankar , Arjan van de Ven , linux-kernel , x86 Subject: Re: [RFC PATCH 00/16] x86/split_lock: Enable #AC exception for split locked accesses Message-ID: <20180621200654.GE13636@worktop.programming.kicks-ass.net> References: <1527435965-202085-1-git-send-email-fenghua.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 29, 2018 at 09:40:09AM -0700, Dave Hansen wrote: > Split-lock-detection is a new hardware feature that generates > alignment-check (#AC) faults to help detect when badly-aligned atomic > instructions might impact whole-system performance. These patches are > primarily targeted at application-level issues, but we can also detect > the same issues in the kernel. Which is nice, Thomas and me spend quite a while searching for a perf event that could tell us about unaligned LOCK insns a few months back and could not find anything useful. > There is a significant interaction > between this feature and firmware because firmware may or may not be > prepared for this feature to be enabled. And allowing firmware to muddle through, instead of drawing a hard line in the sand means we'll be stuck with crap firmware for at least another decade :/ Just say no.