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 4B56BD21262 for ; Thu, 17 Oct 2024 09:18:27 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1t1Mdx-0008EP-Hm; Thu, 17 Oct 2024 05:18:05 -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 1t1Mdw-00089a-12 for qemu-devel@nongnu.org; Thu, 17 Oct 2024 05:18:04 -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 1t1Mdu-0003ox-69 for qemu-devel@nongnu.org; Thu, 17 Oct 2024 05:18:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1729156681; 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=HsB35bQWtFfG0rTwqrYotIUg9wjZsaqXQKsMYUvneNA=; b=hE6hmrDrtqAFGLhYJ8KS4uQ+AclQ+95V4MS82c24ZiFbdcxa5JqCl2VTDNrpouVJ/05ERC ArJ43PSo+DIcTMhRg1RRjDWNnPv1OwtnwEjDsEuW/jPCc784+QmNIFDX3UTSEmkaUAQtLm DE6jpZ8gOsazQuoDEcW2nj2YGm0yJaU= 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-530-VoY5jZLPPQKbKRajasW5CA-1; Thu, 17 Oct 2024 05:18:00 -0400 X-MC-Unique: VoY5jZLPPQKbKRajasW5CA-1 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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5E55219560B8 for ; Thu, 17 Oct 2024 09:17:59 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.94]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DC68D1956086; Thu, 17 Oct 2024 09:17:56 +0000 (UTC) Date: Thu, 17 Oct 2024 10:17:53 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Albert Esteve Cc: qemu-devel@nongnu.org, dbassey@redhat.com, Stefano Garzarella , "Michael S. Tsirkin" Subject: Re: [PATCH] vhost-user: fix shared object return values Message-ID: References: <20241016090606.2358056-1-aesteve@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/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 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: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.038, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=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: 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 Thu, Oct 17, 2024 at 11:12:32AM +0200, Albert Esteve wrote: > On Thu, Oct 17, 2024 at 10:44 AM Daniel P. Berrangé wrote: > > > > On Wed, Oct 16, 2024 at 11:06:06AM +0200, Albert Esteve wrote: > > > VHOST_USER_BACKEND_SHARED_OBJECT_ADD and > > > VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE state > > > in the spec that they return 0 for successful > > > operations, non-zero otherwise. However, > > > implementation relies on the return types > > > of the virtio-dmabuf library, with opposite > > > semantics (true if everything is correct, > > > false otherwise). Therefore, current implementaion > > > violates the specification. > > > > > > Revert the logic so that the implementation > > > of the vhost-user handling methods matches > > > the specification. > > > > > > Fixes: 043e127a126bb3ceb5fc753deee27d261fd0c5ce > > > Fixes: 160947666276c5b7f6bca4d746bcac2966635d79 > > > Signed-off-by: Albert Esteve > > > --- > > > hw/virtio/vhost-user.c | 8 ++++---- > > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > > > index 00561daa06..90917352a4 100644 > > > --- a/hw/virtio/vhost-user.c > > > +++ b/hw/virtio/vhost-user.c > > > @@ -1607,7 +1607,7 @@ vhost_user_backend_handle_shared_object_add(struct vhost_dev *dev, > > > QemuUUID uuid; > > > > > > memcpy(uuid.data, object->uuid, sizeof(object->uuid)); > > > - return virtio_add_vhost_device(&uuid, dev); > > > + return !virtio_add_vhost_device(&uuid, dev); > > > } > > > > This virtio_add_vhost_device() method returns a bool, but this > > vhost_user_backend_handle_shared_object_add() method returns > > an int, but fills that int with an inverted bool value. The > > caller then assigns the return value to an int, but then > > interprets the int as a bool, and assigns that bool result > > to an u64. > > > > This call chain is madness :-( > > TBF most of the madness is part of the already existing > handling infrastructure. > vhost_user_backend_handle_shared_object_add() > returns an int to be consistent with other handling > functions. > > > > > Change vhost_user_backend_handle_shared_object_add to return > > a bool to reduce the madness IMHO. > > Changing it to bool would make it inconsistent > wrt other handlers, and the casting would happen nonetheless > on assignment. Not sure if that is an improvement. Well when the caller does payload.u64 = !!ret; it is saying that it only cares about the values being 0 or 1. So how about just making these methods return 0 or 1 then. > > > > > > > > > static int > > > @@ -1623,16 +1623,16 @@ vhost_user_backend_handle_shared_object_remove(struct vhost_dev *dev, > > > struct vhost_dev *owner = virtio_lookup_vhost_device(&uuid); > > > if (dev != owner) { > > > /* Not allowed to remove non-owned entries */ > > > - return 0; > > > + return -EPERM; > > > } > > > break; > > > } > > > default: > > > /* Not allowed to remove non-owned entries */ > > > - return 0; > > > + return -EPERM; > > > } > > > > > > - return virtio_remove_resource(&uuid); > > > + return !virtio_remove_resource(&uuid); > > > } > > > > These return values are inconsistent. > > > > In some places you're returning a negative errno, but in this > > last place you're returning true or false, by calling > > virtio_remove_resource which is a 'bool' method & inverting it. > > Well, specification only distinguish between zero and non-zero values. > But for clarity, I guess I could do something like: > ``` > if (!virtio_remove_resource(&uuid)) { > return -EINVAL; > } > > return 0; > ``` > > Same for the vhost_user_backend_handle_shared_object_add() > handler (in that case there is no inconsistency with positive or negative > return values, but still better to maintain similar strategy for all > handlers). Returning an errno value, when the caller only wants 0 or 1 is pointless. 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 :|