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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AFEDCC83F1A for ; Mon, 21 Jul 2025 14:08:24 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1udrAz-0000E2-9m; Mon, 21 Jul 2025 10:07:35 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1udr9t-0005ZX-EO for qemu-devel@nongnu.org; Mon, 21 Jul 2025 10:06:26 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1udr9o-0005hr-Vc for qemu-devel@nongnu.org; Mon, 21 Jul 2025 10:06:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753106778; 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=CokC7rm30BVpMN/1DOHYN6IsyXcOUBpsYjNn/hU+iJs=; b=dea1NDmb5+4px5J2LTRjRbKQzi9lz28GPlI8WYJRcMHTiLuYlpnaNpWMGQRnrTp2KqzwsS bEPL0UNWETG2ZuSn2u+RbsQoYuMPw7Un03Umqud67Ci7yXecrBDq9C8GIXKnqreUoFebYg 1iHnc8BgXfjGe9jITAF3BEZ8bTnJ294= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-613-MhVm10qHO_y2vs3DHs34TA-1; Mon, 21 Jul 2025 10:06:15 -0400 X-MC-Unique: MhVm10qHO_y2vs3DHs34TA-1 X-Mimecast-MFC-AGG-ID: MhVm10qHO_y2vs3DHs34TA_1753106772 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9BF15180026D; Mon, 21 Jul 2025 14:06:11 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.213]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D9E0819560AB; Mon, 21 Jul 2025 14:06:02 +0000 (UTC) Date: Mon, 21 Jul 2025 15:05:59 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Arun Menon Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" , Marcel Apfelbaum , Cornelia Huck , Halil Pasic , Eric Farman , Richard Henderson , David Hildenbrand , Ilya Leoshkevich , Thomas Huth , Christian Borntraeger , Paolo Bonzini , Fam Zheng , Nicholas Piggin , Daniel Henrique Barboza , Harsh Prateek Bora , Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Peter Xu , Fabiano Rosas , Hailiang Zhang , Steve Sistare , qemu-s390x@nongnu.org, qemu-ppc@nongnu.org, Stefan Berger , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Alex =?utf-8?Q?Benn=C3=A9e?= , Akihiko Odaki , Dmitry Osipenko , Matthew Rosato Subject: Re: [PATCH v6 23/24] migration: Add error-parameterized function variants in VMSD struct Message-ID: References: <20250721-propagate_tpm_error-v6-0-fef740e15e17@redhat.com> <20250721-propagate_tpm_error-v6-23-fef740e15e17@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.926, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Jul 21, 2025 at 07:24:23PM +0530, Arun Menon wrote: > Hi, > Thank you for the review. > > On Mon, Jul 21, 2025 at 02:32:48PM +0100, Daniel P. Berrangé wrote: > > On Mon, Jul 21, 2025 at 04:59:28PM +0530, Arun Menon wrote: > > > - We need to have good error reporting in the callbacks in > > > VMStateDescription struct. Specifically pre_save, post_save, > > > pre_load and post_load callbacks. > > > - It is not possible to change these functions everywhere in one > > > patch, therefore, we introduce a duplicate set of callbacks > > > with Error object passed to them. > > > - So, in this commit, we implement 'errp' variants of these callbacks, > > > introducing an explicit Error object parameter. > > > - This is a functional step towards transitioning the entire codebase > > > to the new error-parameterized functions. > > > - Deliberately called in mutual exclusion from their counterparts, > > > to prevent conflicts during the transition. > > > - New impls should preferentally use 'errp' variants of > > > these methods, and existing impls incrementally converted. > > > The variants without 'errp' are intended to be removed > > > once all usage is converted. > > > > > > Signed-off-by: Arun Menon > > > --- > > > include/migration/vmstate.h | 11 +++++++++++ > > > migration/vmstate.c | 47 +++++++++++++++++++++++++++++++++++++++------ > > > 2 files changed, 52 insertions(+), 6 deletions(-) > > > > > > > > diff --git a/migration/vmstate.c b/migration/vmstate.c > > > index 288b57e1ed778cce21247b64d5e97dfef41ad586..d96908d12ccffaef421e5d399a48e26cada2cb77 100644 > > > --- a/migration/vmstate.c > > > +++ b/migration/vmstate.c > > > > > @@ -524,7 +548,12 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, > > > if (ret) { > > > error_setg(errp, "Save of field %s/%s failed", > > > vmsd->name, field->name); > > > - if (vmsd->post_save) { > > > + if (vmsd->post_save_errp) { > > > + ret = vmsd->post_save_errp(opaque, &local_err); > > > + if (ret < 0) { > > > + error_propagate(errp, local_err); > > > + } > > > > This is still broken. 'errp' is already set a few lines earlier, so you > > can't propagate a new error over the top > > I was wondering that we should preserve the first error that was encountered. > So even if local_err was set, and in case errp already has an error, then it will > be a no-op and local_err will be freed. We know that 'local_err' is definitely set when 'post_save_errp' is called, because there's a call to 'error_setg' right above it. > > > + } else if (vmsd->post_save) { > > > vmsd->post_save(opaque); > > > } ... pre-existing mistake not checking return value of post_save. > > > return ret; > > > @@ -552,7 +581,13 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, > > > > > > ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc, errp); > > > > > > - if (vmsd->post_save) { > > > + if (vmsd->post_save_errp) { > > > + int ps_ret = vmsd->post_save_errp(opaque, &local_err); > > > + if (!ret && ps_ret) { > > > + ret = ps_ret; > > > + error_propagate(errp, local_err); > > > + } > > > > Again, propagating over the top of an existing error > > Sorry, correct me if I am wrong. > Since we have 'if (!ret && ps_ret)' , > if vmstate_subsection_save() fails, the above condition will not hold true. > Only if the first function call vmstate_subsection_save() is successful and the second one > post_save_errp() fails then we try to propagate, again hoping to preserve the first error. Opps, yes, you're right - I missed the 'ps_ret' check. That means this code is a memory leak when 'ret' is non-zero, as nothing frees 'local_err' in that case. > > > > > > + } else if (vmsd->post_save) { > > > int ps_ret = vmsd->post_save(opaque); > > > if (!ret && ps_ret) { > > > ret = ps_ret; > > > > > > -- > > > 2.50.0 > > > > > > > > > > With regards, > > Daniel > > -- > > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > > |: https://libvirt.org -o- https://fstop138.berrange.com :| > > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| > > > > Regards, > Arun Menon > With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|