From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5CB1D606A31A for ; Thu, 29 Oct 2026 15:35:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=Q0tcfZsU Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xMSA6-0004Ow-9Y; Thu, 29 Oct 2026 11:35:30 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xMSA3-0004Lf-H2 for qemu-devel@nongnu.org; Thu, 29 Oct 2026 11:35:27 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xMSA0-0005JA-Jg for qemu-devel@nongnu.org; Thu, 29 Oct 2026 11:35:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1793288123; h=from:from:reply-to: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=Iv1U2dZd1BB1z1IQ2jlltvoEOnaBXVnyfqCjSRZ0Ez8=; b=Q0tcfZsUKlVkylvLqFYIVfHSrML0gV62O/+f7l05CPKe1joOVkAdjmBPeOFdhKgDmC47LL lY+R54V6zW8GRFtOlcaJdw8BLzIIMckA9zJvhEbG2wgkj60VXTU7TDEiXq0NDqdOTykY7F 0A/qWaOFppThzjiDb19sAu8KyjtK1r0= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-338-xCc49j7WNWCxI1uX8EDgyQ-1; Thu, 29 Oct 2026 11:35:13 -0400 X-MC-Unique: xCc49j7WNWCxI1uX8EDgyQ-1 X-Mimecast-MFC-AGG-ID: xCc49j7WNWCxI1uX8EDgyQ_1793288112 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id AF7EB19540CF; Thu, 29 Oct 2026 15:35:11 +0000 (UTC) Received: from redhat.com (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6358C18004D2; Thu, 29 Oct 2026 15:35:08 +0000 (UTC) Date: Thu, 29 Oct 2026 15:35:05 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Cc: qemu-devel@nongnu.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Michael Roth , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Fabiano Rosas , Richard Henderson , "Dr. David Alan Gilbert" , Paolo Bonzini , Pierrick Bouvier , Eric Blake , Laurent Vivier Subject: Re: [PATCH 07/21] util: introduce 'tldr', a system data recorder for crash handling Message-ID: References: <20261015112044.1999748-1-berrange@redhat.com> <20261015112044.1999748-8-berrange@redhat.com> <87ecd8gba1.fsf@pond.sub.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87ecd8gba1.fsf@pond.sub.org> User-Agent: Mutt/2.4.2 (2026-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 5 X-Spam_score: 0.5 X-Spam_bar: / X-Spam_report: (0.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, GB_FAKE_RF=0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-12.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Oct 29, 2026 at 09:29:26AM +0100, Markus Armbruster wrote: > Daniel P. BerrangΓ© writes: > > > Introduce a new subsystem "tldr" aka "thrifty live data recorder" > > that will be able to continuously collect certain information at > > runtime and dump that in a crash report when QEMU exits abnormally. > > As a second use case, it will support manual triggering on interesting > > events such as guest OS panic. > > What's manual about that? Manual in the sense that the mgmt app has to explicitly request the data recorder contents when a guest OS panics, vs automatic dump when QEMU dies with a fatal signal. > > diff --git a/qapi/qom.json b/qapi/qom.json > > index 49f222796ab..1c9031fba9a 100644 > > --- a/qapi/qom.json > > +++ b/qapi/qom.json > > @@ -1233,6 +1233,19 @@ > > 'data': { '*pretty': 'bool', > > '*close-action': 'MonitorQMPCloseAction' } } > > > > +## > > +# @QTLDRConfigProperties: > > +# Configuration for data recorder > > +# > > +# @crash-target: fully qualified path to perserve data recorder > > +# contents on QEMU crash > > What's a "fully qualified path"? > > Do you mean what POSIX calls "absolute pathname"? Yes. > > diff --git a/qemu-options.hx b/qemu-options.hx > > index 2f6863180b0..2f63d86b635 100644 > > --- a/qemu-options.hx > > +++ b/qemu-options.hx > > @@ -6682,6 +6682,20 @@ SRST > > :: > > > > (qemu) qom-set /objects/iothread1 poll-max-ns 100000 > > + > > + > > + ``-object tldr-config,id=id,crash-target=path`` > > + Creating the ``tldr-config`` object enables the thrifty live data > > + recorder, which continuously captures important information about > > + the operation of the QEMU process. When a SIGSEGV, SIGBUS, > > + SIGILL, SIGFPE or SIGABRT are seen the contents of the data > > + recorder will be dumped to the stderr stream. If the > > + ``crash-target`` parameter was given, that specifies a fully > > + qualified file path to write the dump to instead of stderr. > > + > > + The ``tldr-config`` object can be added at initial startup > > + or via QMP at runtime. Once created, however, it is not > > + permitted to disable it. > > Call the object "tldr"? Yes, that's an option. > > diff --git a/util/tldr-internal.h b/util/tldr-internal.h > > new file mode 100644 > > index 00000000000..193d8425eee > > --- /dev/null > > +++ b/util/tldr-internal.h > > @@ -0,0 +1,21 @@ > > +/* > > + * SPDX-License-Identifier: GPL-2.0-or-later > > + * > > + * TL;DR: Thrifty Live Data Recorder > > + * > > + * Copyright (C) 2026 Red Hat Inc. > > + */ > > + > > +#ifndef QEMU_TLDR_INTERNAL_H__ > > +#define QEMU_TLDR_INTERNAL_H__ > > + > > +#include "qemu/tldr.h" > > + > > +#define QTLDR_DUMP_LEADER "\n🚨🚨🚨 QEMU Data Recorder Start 🚨🚨🚨\n" > > +#define QTLDR_DUMP_TRAILER "\n🚨🚨🚨 QEMU Data Recorder End 🚨🚨🚨\n\n" > > +#define QTLDR_DUMP_TRIGGER_PREFIX "\nπŸ” Trigger:" > > +#define QTLDR_DUMP_OPEN_ERROR "πŸ”₯ Unable to dump to '" > > The emojis make the dump file UTF-8. Fine, I guess? Personally I consider UTF-8 to be acceptable/expected to work for any OS platform since the mid 2000s, certainly for platforms that QEMU targets. With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|