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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 F0D54C433E0 for ; Thu, 4 Jun 2020 13:36:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF701206E6 for ; Thu, 4 Jun 2020 13:36:13 +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="NyXrTY6m" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728651AbgFDNgM (ORCPT ); Thu, 4 Jun 2020 09:36:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45146 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728555AbgFDNgM (ORCPT ); Thu, 4 Jun 2020 09:36:12 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 07ED6C08C5C0 for ; Thu, 4 Jun 2020 06:36:12 -0700 (PDT) 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=ZMaPZF+V7CfNghVvBnaqgqTzlHf579PrFooouexO+HQ=; b=NyXrTY6mOBpfJPW9mEVjz8IdPn ou/ApnWtA/3t/wrqRoMll4Of8KRD/Kbm4pjgarwN0XSTZp8x2GDHBcNsCiXYoqG+ksI/Z32KHVW7p Y8BwJINAVFWHBlqHIXN6rCuftZ5H7qGIdnpfq0XIwahFYJn0itcQuHL2MzCECHi1jO6m7rm86hrWP SKxdYNQNYDhDlDUifnnyNpU3xUJpS3ueqpHS0ym+F2PHesd3KQpt45i9bsT68Ocp6QwZu46iJ/ZLR X6RWCIlYrTN18Kx0ZZXFm4/i4h8hrIQMPvdv0wFwq+/3EbdznTvulmXu3L6dcZjqaUR+lbhFikJEC uBx5CKCQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jgq28-0003ym-1p; Thu, 04 Jun 2020 13:35:48 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 95AF43035D4; Thu, 4 Jun 2020 15:35:45 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 3A40620D6E7D9; Thu, 4 Jun 2020 15:35:45 +0200 (CEST) Date: Thu, 4 Jun 2020 15:35:45 +0200 From: Peter Zijlstra To: Paolo Bonzini Cc: Andrew Cooper , Thomas Gleixner , LKML , Andy Lutomirski , X86 ML , "Paul E. McKenney" , Alexandre Chartre , Frederic Weisbecker , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon , Tom Lendacky , Wei Liu , Michael Kelley , Jason Chen CJ , Zhao Yakui , "H. Peter Anvin" Subject: Re: [patch V9 00/39] x86/entry: Rework leftovers (was part V) Message-ID: <20200604133545.GB3976@hirez.programming.kicks-ass.net> References: <20200521200513.656533920@linutronix.de> <5e68aa83-feac-2aa7-10ee-aebebc60c83e@citrix.com> <20200522211706.GZ2483@worktop.programming.kicks-ass.net> <83474edd-195f-f10b-9fe9-8ee168344e29@citrix.com> <20200604132537.GA3976@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 04, 2020 at 03:29:26PM +0200, Paolo Bonzini wrote: > On 04/06/20 15:25, Peter Zijlstra wrote: > > It being enabled through IA32_DEBUGCTL instead of through DR7 means that > > the current code doesn't disable it and this then means we can have > > nested #DB again. > > /me bangs head on door > > > Who sodding throught this was a good idea ?! What happened to #AC that > > SLD currently uses? > > It was per-core and (presumably) considered unfixable? Yeah, but I don't see how changing the exception vector helps with that. #DB is an IST, and it must be, because of that lovely MOV SS thing. #AC has none of that, _please_ use #AC.