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=-6.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 E49F9C433E1 for ; Tue, 28 Jul 2020 10:49:51 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id AF89B20775 for ; Tue, 28 Jul 2020 10:49:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cLevW/xz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AF89B20775 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58130 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k0NB9-0005Xx-20 for qemu-devel@archiver.kernel.org; Tue, 28 Jul 2020 06:49:51 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56642) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k0NAb-00057T-SW for qemu-devel@nongnu.org; Tue, 28 Jul 2020 06:49:17 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:21218 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1k0NAZ-0004Ku-QS for qemu-devel@nongnu.org; Tue, 28 Jul 2020 06:49:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595933354; 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=DmT1eI01BzeIIMsat94yL5ZlTrQNy/w8csJXnhioZjk=; b=cLevW/xzLi87DWB9ebdU8pCs8oJPMKro+hK5DbXxxPeetqA0As47rPpK4sLyxWylv7OVGb ODcTCMkQ5yc3CysXgB64npElSqxCYZFJ5rbAh4LujPiBReUs7Xx/D1Cm8EoQle3sHOYiFg Fk3WeW7LBk23qNy/IC8fz/c8+S89dy0= 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-472-ZzZV_khqNK-cJj7nTf0Xeg-1; Tue, 28 Jul 2020 06:49:05 -0400 X-MC-Unique: ZzZV_khqNK-cJj7nTf0Xeg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1784E107ACCA; Tue, 28 Jul 2020 10:49:04 +0000 (UTC) Received: from gondolin (ovpn-113-21.ams2.redhat.com [10.36.113.21]) by smtp.corp.redhat.com (Postfix) with ESMTP id 212CC712C2; Tue, 28 Jul 2020 10:48:52 +0000 (UTC) Date: Tue, 28 Jul 2020 12:48:50 +0200 From: Cornelia Huck To: Halil Pasic Subject: Re: [RFC v2 2/3] libvhost-user: handle endianness as mandated by the spec Message-ID: <20200728124850.7c15eade.cohuck@redhat.com> In-Reply-To: <20200721184456.1305ca0b.pasic@linux.ibm.com> References: <20200717092929.19453-1-mhartmay@linux.ibm.com> <20200717092929.19453-3-mhartmay@linux.ibm.com> <20200721093942-mutt-send-email-mst@kernel.org> <20200721184456.1305ca0b.pasic@linux.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.61; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/28 06:02:02 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Daniel P. =?UTF-8?B?QmVycmFuZ8Op?=" , "Michael S. Tsirkin" , qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , Marc Hartmayer , Stefan Hajnoczi , =?UTF-8?B?TWFyYy1BbmRyw6k=?= Lureau Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 21 Jul 2020 18:44:56 +0200 Halil Pasic wrote: > On Tue, 21 Jul 2020 09:40:10 -0400 > "Michael S. Tsirkin" wrote: > > > On Fri, Jul 17, 2020 at 11:29:28AM +0200, Marc Hartmayer wrote: > > > Since virtio existed even before it got standardized, the virtio > > > standard defines the following types of virtio devices: > > > > > > + legacy device (pre-virtio 1.0) > > > + non-legacy or VIRTIO 1.0 device > > > + transitional device (which can act both as legacy and non-legacy) > > > > > > Virtio 1.0 defines the fields of the virtqueues as little endian, > > > while legacy uses guest's native endian [1]. Currently libvhost-user > > > does not handle virtio endianness at all, i.e. it works only if the > > > native endianness matches with whatever is actually needed. That means > > > things break spectacularly on big-endian targets. Let us handle virtio > > > endianness for non-legacy as required by the virtio specification > > > [1]. We will fence non-legacy virtio devices with the upcoming patch. > > > > > > [1] https://docs.oasis-open.org/virtio/virtio/v1.1/cs01/virtio-v1.1-cs01.html#x1-210003 > > > > > > Signed-off-by: Marc Hartmayer > > > > > > --- > > > Note: As we don't support legacy virtio devices > > > > Who's "we" in this sentence? vhost user supports legacy generally ... > > In that sentence "we" is the library "libvhost-user". I would like > to avoid s390x being an oddball regarding this. Marc's previous > version made an attempt at correct endianness handling for legacy > and non-legacy. That spawned a discussion on how we don't want > legacy devices in this context. This series makes what seemed to be the > consensus reached in that discussion explicit: namely that libvhost-user > does not support legacy-virtio. Can someone please clarify what libvhost-user actually supports? virtio-fs is clearly non-legacy only, but in the changelog I also see a mention of scsi, and that one probably does support legacy? Can we make a distinction along the lines of: - if we are non-legacy, we support any endianness; - if we are legacy, we support little endian host/guest only?