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=-5.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 AE1EFC433E1 for ; Sun, 23 Aug 2020 23:11:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 897F22072D for ; Sun, 23 Aug 2020 23:11:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598224296; bh=BCwIL8BZHn3eI2tqa/kgvc98qVPVBfUsxvsIzZrfJ3g=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=1AcebnnvfkvXZ2bFYlkrcCLcccVYR0WI/hw4BFVpo1vfs4mDoFrWaJIlYve3AkSI5 PLjYfCZPjRASGWNJy1WHHjJISN7fG5zYYhqhMz8gqG+psMW3hBhq+0aiYyUPvglOEj Z7os1FmYlvwJErGzhvJRMtki3xd8nTwGGh6YvSqo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726923AbgHWXLf (ORCPT ); Sun, 23 Aug 2020 19:11:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:40160 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726480AbgHWXLc (ORCPT ); Sun, 23 Aug 2020 19:11:32 -0400 Received: from mail-wm1-f45.google.com (mail-wm1-f45.google.com [209.85.128.45]) (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 35E45221E2 for ; Sun, 23 Aug 2020 23:11:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598224291; bh=BCwIL8BZHn3eI2tqa/kgvc98qVPVBfUsxvsIzZrfJ3g=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=XHNpaLqfzGlDhobM8HCFCbVvtDNvg4cdhZ+xWNXKFGtC3KKyT3kLsK4adLu+O71qc EnOxLyAI+xCEGVSSOEXMZ0jvdWcxgx/AUPen3MBDQjaIjs7yMpa86GtozO5sD7KI2Z ifYhR1pD3eLt57bMZ/2UMjFqBgXmh4H61JJsf9Sw= Received: by mail-wm1-f45.google.com with SMTP id a65so3050045wme.5 for ; Sun, 23 Aug 2020 16:11:31 -0700 (PDT) X-Gm-Message-State: AOAM533bXrsw8/xcDNVH/8hYbCmT3T4bzyDaMQRIvxrU9Pk5FbyKurlO ZjPWSp6bysz7+ZNINs+26TNH+EKueVju6GsE7xdWaw== X-Google-Smtp-Source: ABdhPJz8B6sM7+LM2fthhpeY9wjeM67AlrTus0j2XWe7olFHIGn6T6qEvgzyAhqEGJia10bJyk48lWg8laNqXsQesoI= X-Received: by 2002:a7b:c76e:: with SMTP id x14mr2904019wmk.176.1598224289860; Sun, 23 Aug 2020 16:11:29 -0700 (PDT) MIME-Version: 1.0 References: <20200821093912.815135402@infradead.org> <20200821102053.219655533@infradead.org> In-Reply-To: <20200821102053.219655533@infradead.org> From: Andy Lutomirski Date: Sun, 23 Aug 2020 16:11:18 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 8/8] x86/debug: Remove the historical junk To: Peter Zijlstra Cc: X86 ML , LKML , Kyle Huey , Alexandre Chartre , "Robert O'Callahan" , "Paul E. McKenney" , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Andy Lutomirski , Josh Poimboeuf , Daniel Thompson 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 On Fri, Aug 21, 2020 at 3:21 AM Peter Zijlstra wrote: > > Remove the historical junk and replace it with a WARN and a comment. > > The problem is that even though the kernel only uses TF single-step in > kprobes and KGDB, both of which consume the event before this, > QEMU/KVM has bugs in this area that can trigger this state so we have > to deal with it. Almost acked by me. If you make the change I suggested earlier, then the ->debugreg6 garbage can actually die. --Andy