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=-0.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 47E2EC433E0 for ; Fri, 29 May 2020 08:00:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1580D206F1 for ; Fri, 29 May 2020 08:00:53 +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="aOxHYxBi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726330AbgE2IAw (ORCPT ); Fri, 29 May 2020 04:00:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36478 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725855AbgE2IAv (ORCPT ); Fri, 29 May 2020 04:00:51 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4F7BC03E969 for ; Fri, 29 May 2020 01:00:51 -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=Z6N+AyF//kWKUxyY54RXv1ce3V0l/RXLH14GaVL9d8U=; b=aOxHYxBiL/Ty9S649/vsGw6Y0P iY10FrvXQwRLvHw4+IyGPBPk3BcXLT/7rr4IOI+ljCD4FtYDpvkHlTN2Cz3MkBfOtjo2Zy37W08CC wB2zNxFxD5USgi+/LyGh8Q58B+lPZa2JOpAEPqr4d1YO9ieKkHibmdDCDWnWT9KiH3CHKAG+IBLfq DlTZTMehshT+kghaINdZ22FG0UupONxTxN12Pal0ZBHZx2e7AEIpYpMnlIFAW2/yuJsgN09gQeTNc mi75VXM0EJKZg0czEeCPpBhHXT9nhkfjJj8sRPoRrZ1blaagAlFpWgn1hhIW2XM+p96qU1gQKZFB+ yboAM+0A==; 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 1jeZwV-0001mS-3R; Fri, 29 May 2020 08:00:39 +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 2DD8B3069A1; Fri, 29 May 2020 10:00:36 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 0D965200895A2; Fri, 29 May 2020 10:00:36 +0200 (CEST) Date: Fri, 29 May 2020 10:00:36 +0200 From: Peter Zijlstra To: Lai Jiangshan Cc: Thomas Gleixner , Andy Lutomirski , LKML , X86 ML , Lai Jiangshan , Sean Christopherson , andrew.cooper3@citrix.com, daniel.thompson@linaro.org Subject: Re: [PATCH 0/6] x86/entry: disallow #DB more Message-ID: <20200529080036.GH706495@hirez.programming.kicks-ass.net> References: <20200528201937.038455891@infradead.org> <20200528224835.GU2483@worktop.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 Fri, May 29, 2020 at 07:05:54AM +0800, Lai Jiangshan wrote: > On Fri, May 29, 2020 at 6:48 AM Peter Zijlstra wrote: > > > > On Fri, May 29, 2020 at 06:42:46AM +0800, Lai Jiangshan wrote: > > > On Fri, May 29, 2020 at 4:25 AM Peter Zijlstra wrote: > > > > > > > > These patches disallow #DB during NMI/#MC and allow removing a lot of fugly code. > > > > > > > > > > Hello > > > > > > Will #DB be allowed in #DF? > > > > No, that whole thing is noinstr. > > But it calls many functions, including die(), panic(). > We don't want #DB to interfere how it die() and panic(). > Since it is in fragile #DF, the #DB may mess it up and > make #DF fails to report and die. The only recoverable #DF is the ESPFIX shit. If we do not take that, we're on the way to panic(), I really can't be arsed if you crash the box before that, we're going to die anyway.