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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 D05EAC433E0 for ; Tue, 30 Jun 2020 11:00:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A39B5207E8 for ; Tue, 30 Jun 2020 11:00:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="U+gdJ3Kk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732767AbgF3LAx (ORCPT ); Tue, 30 Jun 2020 07:00:53 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:57778 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732578AbgF3LAw (ORCPT ); Tue, 30 Jun 2020 07:00:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593514850; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YPlk3hHtIg/3QWwatoM9sTH8lwQ8W3Qj2pLZMQRNWLg=; b=U+gdJ3KkjXqCHGAZbdF8EWlf+TioLjJT0UdbBivshMr970ZGoWwITsjvQtPMX5zuEbHFCg VLkNSIFoc/wHRFT57Cq5jal7cqtccr1VgtsfZjp5zRw43KVn9BC4HtPvU7KV3zL3YBhKVR 6jOhYXKh8oP14nz0c/BnEKaFuaq4zu0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-407-DRmRpGz4MN2CHU7GK9keoA-1; Tue, 30 Jun 2020 07:00:45 -0400 X-MC-Unique: DRmRpGz4MN2CHU7GK9keoA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B4FA4188363A; Tue, 30 Jun 2020 11:00:41 +0000 (UTC) Received: from prarit.bos.redhat.com (prarit-guest.7a2m.lab.eng.bos.redhat.com [10.16.222.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id F3D8260CD1; Tue, 30 Jun 2020 11:00:35 +0000 (UTC) Subject: Re: [PATCH v5] x86/split_lock: Sanitize userspace and guest error output To: linux-kernel@vger.kernel.org Cc: Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Tony Luck , "Peter Zijlstra (Intel)" , Rahul Tanwar , Xiaoyao Li , Ricardo Neri , Dave Hansen References: <20200616113250.2061-1-prarit@redhat.com> From: Prarit Bhargava Message-ID: <11733c3d-056a-e723-c4fe-ec3f55c1e94a@redhat.com> Date: Tue, 30 Jun 2020 07:00:35 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20200616113250.2061-1-prarit@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Just re-pinging on this. P. On 6/16/20 7:32 AM, Prarit Bhargava wrote: > There are two problems with kernel messages in fatal mode that were found > during testing of guests and userspace programs. > > The first is that no kernel message is output when the split lock detector > is triggered with a userspace program. As a result the userspace process > dies from receiving SIGBUS with no indication to the user of what caused > the process to die. > > The second problem is that only the first triggering guest causes a kernel > message to be output because the message is output with pr_warn_once(). > This also results in a loss of information to the user. > > While fixing these I noticed that the same message was being output > three times so I'm cleaning that up too. > > Fix fatal mode output, and use consistent messages for fatal and > warn modes for both userspace and guests. > > Co-developed-by: Sean Christopherson > Signed-off-by: Sean Christopherson > Signed-off-by: Prarit Bhargava > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: Borislav Petkov > Cc: x86@kernel.org > Cc: "H. Peter Anvin" > Cc: Tony Luck > Cc: "Peter Zijlstra (Intel)" > Cc: Sean Christopherson > Cc: Rahul Tanwar > Cc: Xiaoyao Li > Cc: Ricardo Neri > Cc: Dave Hansen > --- > v2: Do not output a message if CPL 3 Alignment Check is turned on (xiaoyao.li) > v3: refactor code (sean.j.christopherson) > v4: Fix Sign off (sean.j.christopherson) > v5: Fix Sign off (sean.j.christopherson) > > arch/x86/kernel/cpu/intel.c | 22 ++++++++++------------ > 1 file changed, 10 insertions(+), 12 deletions(-) > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c > index 63926c94eb5f..3a373f0be674 100644 > --- a/arch/x86/kernel/cpu/intel.c > +++ b/arch/x86/kernel/cpu/intel.c > @@ -1074,11 +1074,14 @@ static void split_lock_init(void) > split_lock_verify_msr(sld_state != sld_off); > } > > -static void split_lock_warn(unsigned long ip) > +static bool handle_split_lock(unsigned long ip) > { > - pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n", > + pr_warn("#AC: %s/%d took a split_lock trap at address: 0x%lx\n", > current->comm, current->pid, ip); > > + if (sld_state != sld_warn) > + return false; > + > /* > * Disable the split lock detection for this task so it can make > * progress and set TIF_SLD so the detection is re-enabled via > @@ -1086,18 +1089,13 @@ static void split_lock_warn(unsigned long ip) > */ > sld_update_msr(false); > set_tsk_thread_flag(current, TIF_SLD); > + return true; > } > > bool handle_guest_split_lock(unsigned long ip) > { > - if (sld_state == sld_warn) { > - split_lock_warn(ip); > + if (handle_split_lock(ip)) > return true; > - } > - > - pr_warn_once("#AC: %s/%d %s split_lock trap at address: 0x%lx\n", > - current->comm, current->pid, > - sld_state == sld_fatal ? "fatal" : "bogus", ip); > > current->thread.error_code = 0; > current->thread.trap_nr = X86_TRAP_AC; > @@ -1108,10 +1106,10 @@ EXPORT_SYMBOL_GPL(handle_guest_split_lock); > > bool handle_user_split_lock(struct pt_regs *regs, long error_code) > { > - if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal) > + if (regs->flags & X86_EFLAGS_AC) > return false; > - split_lock_warn(regs->ip); > - return true; > + > + return handle_split_lock(regs->ip); > } > > /* >