Received: by 2002:a25:ad19:0:0:0:0:0 with SMTP id y25csp2738092ybi; Thu, 18 Jul 2019 13:28:47 -0700 (PDT) X-Google-Smtp-Source: APXvYqx0t+sB7bHsVmnMMvRg5gDc2gDnmaWAKK9burZS/LwUgTDf+K4IIzqEOjQXKRJ1hlFNara4 X-Received: by 2002:a63:1908:: with SMTP id z8mr48392535pgl.433.1563481727413; Thu, 18 Jul 2019 13:28:47 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1563481727; cv=none; d=google.com; s=arc-20160816; b=R9G+108oAvD6DwimBa0KA90cPMfggFDnPFb4t8bVpOG0LGUjr0B9nd24zg1uImR7W1 IjfB3LghTBGMhX7j+T8M9ZpEfz/LtEthEkLsirDJqu2Pdx8XpJC2kIjikO1BEat2gdqZ J+vP5Fpg5cSlgojzg7z0QTDkXVVo79lO4zL3HqC7gkwaOow3ZUi2M4FnItsE9HTZei7I xqFNKtpj52wk07o1DaaQWCXfINguOzXv/Ztw7q1HZunf5V/Dy9cMSQJbLkkVTRmroNMQ qlDfw8jwulQI7mNuVTMV192iQppYVcYyKK4p0evxb1Ar7N8S3Ee4orfRGZoyGyxefxi1 D0EA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:dkim-signature; bh=cplojg0HvfQBkpNyld2ETJzKKPXdpSis6WXfmSXsQJg=; b=M+zDPiaTUi8M8UkjCiCoj3BZCuCae4Rnj0rMZPmzE1um2a1ujPNqhFLa3ZoGm1TNct YVbwwRc8MVrRvj5Uo6+pNlEuTPPxT73liLd6qj5Bvzi67eF8/dao3SpesNNFxz6Op1SG SnBEzrJufLTwCz5eE5kPYdAs6XNnBAHNJ/HDHcDccJzxfIZ4OGVdyQ5qtf+wMfxsP2Ga U2KHkWmXHUnoe/xdJ58sSAvHY0hZGi9Xw1n7zfLzoLuIWdEGYpBIoCOj5IO2k2d91uBS o9f7+oDenem3omr++ef/Np9oTo+2QRl1smNN9qZ9evk87oO7GPHpl5uOkK/F1ckOfMOU 6Nvw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=oBG0Juae; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id q19si1656971pgv.31.2019.07.18.13.28.31; Thu, 18 Jul 2019 13:28:47 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=oBG0Juae; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403843AbfGRU1i (ORCPT + 99 others); Thu, 18 Jul 2019 16:27:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:36274 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727687AbfGRU1h (ORCPT ); Thu, 18 Jul 2019 16:27:37 -0400 Received: from mail-wm1-f54.google.com (mail-wm1-f54.google.com [209.85.128.54]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A4E852184B for ; Thu, 18 Jul 2019 20:27:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563481656; bh=cplojg0HvfQBkpNyld2ETJzKKPXdpSis6WXfmSXsQJg=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=oBG0Juaeg3epDPdx+6GqKNV1yBx7KZYoyWUmq6TrNvzX7CBY6kSIGywzXksU2j2BK owkOVT6bJ6yk7KJTchvwIFL+dxgtsRKR8P6oQdASEGNA4lk3hHMmCTFikU4S/UxRx0 JYVvuNHP4HpXt5elONtyHlWzRC/QK6OKiqjQ42EE= Received: by mail-wm1-f54.google.com with SMTP id w9so22279604wmd.1 for ; Thu, 18 Jul 2019 13:27:36 -0700 (PDT) X-Gm-Message-State: APjAAAUEsnnhq5b/BEeLRdiu8Pnh3j9I4q7WSAVSPw/7/u8jrn0LUgph opavepgvhfSe4YfHjBRZYOXNL9r6giYjBGhFpVodaQ== X-Received: by 2002:a7b:c4d2:: with SMTP id g18mr44091396wmk.79.1563481655228; Thu, 18 Jul 2019 13:27:35 -0700 (PDT) MIME-Version: 1.0 References: <20190711114054.406765395@infradead.org> <4c71e14d-3a32-c3bb-8e3b-6e5100853192@oracle.com> <97cdd0af-95cc-2583-dc19-129b20809110@oracle.com> In-Reply-To: From: Andy Lutomirski Date: Thu, 18 Jul 2019 13:27:23 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 0/6] Tracing vs CR2 To: Eiichi Tsukata Cc: Vegard Nossum , Peter Zijlstra , Thomas Gleixner , Borislav Petkov , Ingo Molnar , Steven Rostedt , Andrew Lutomirski , Linus Torvalds , linux_lkml_grp@oracle.com, "H. Peter Anvin" , Dave Hansen , Juergen Gross , LKML , He Zhe , Joel Fernandes Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all- I suspect that a bunch of the bugs you're all finding boil down to: - Nested debug exceptions could corrupt the outer exception's DR6. - Nested debug exceptions in which *both* exceptions came from the kernel were probably all kinds of buggy - Data breakpoints in bad places in the kernel were bad news Could you give this not-quite-finished series a try? https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/