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_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 E8F16C43331 for ; Thu, 2 Apr 2020 20:48:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AAE2E2077D for ; Thu, 2 Apr 2020 20:48:47 +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="cqpaQ2QO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389145AbgDBUsq (ORCPT ); Thu, 2 Apr 2020 16:48:46 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:36708 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727412AbgDBUsq (ORCPT ); Thu, 2 Apr 2020 16:48:46 -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; bh=7byunhOigmKgF2sOm4YN5Lry/ZYZDusqM73GCeYnAPo=; b=cqpaQ2QO6mRhZCASxfC8JL0RxH gEglXo7uGL17beLgCvsDmXbxPXgizBfS7HDZl2fE2KwNXzcJWeDiGu962SufoVcYPy/U9v/LC0ya1 uqtjKsqj5I/Sc6KvJ+wsm4TX2jyWeURAU5aTk8zjaCbccgxtXch9L6VBumZLR/jIcxInJRVPbCDf7 wKEc8s8uJp7f7knqJe5pJK+L+Xl2VzujB4nBuTVWPsZ6g9D4ZEZ4HKmAerVwGmWlt4bq/29q2X6LE jL9U4jNyOReHpD3FAXPj7lZc45cFMHdIFI+KI1lBhrvpkA2Sc49sn4Uo+T/9sruSScErzYsnSSzRv rPsH3NCA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jK6l9-000322-Ll; Thu, 02 Apr 2020 20:48:19 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id E3B6B9834EB; Thu, 2 Apr 2020 22:48:16 +0200 (CEST) Date: Thu, 2 Apr 2020 22:48:16 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: Sean Christopherson , x86@kernel.org, "Kenneth R . Crudup" , Paolo Bonzini , Fenghua Yu , Xiaoyao Li , Nadav Amit , Thomas Hellstrom , Tony Luck , Jessica Yu , Steven Rostedt , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] KVM: VMX: Extend VMX's #AC interceptor to handle split lock #AC in guest Message-ID: <20200402204816.GJ2452@worktop.programming.kicks-ass.net> References: <20200402124205.334622628@linutronix.de> <20200402155554.27705-1-sean.j.christopherson@intel.com> <20200402155554.27705-4-sean.j.christopherson@intel.com> <87sghln6tr.fsf@nanos.tec.linutronix.de> <20200402174023.GI13879@linux.intel.com> <87h7y1mz2s.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87h7y1mz2s.fsf@nanos.tec.linutronix.de> 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 Thu, Apr 02, 2020 at 10:07:07PM +0200, Thomas Gleixner wrote: If we're doing wish lists, I have one more ;-) > TBH, the more I learn about this, the more I tend to just give up on > this whole split lock stuff in its current form and wait until HW folks > provide something which is actually usable: > > - Per thread > - Properly distinguishable from a regular #AC via error code - is an actual alignment check. That is, disallow all unaligned LOCK prefixed ops, not just those that happen to straddle a cacheline.