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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 BBB8BC433E0 for ; Thu, 25 Jun 2020 10:40:57 +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 8225720773 for ; Thu, 25 Jun 2020 10:40:57 +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="AHU94Y1S" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8225720773 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]:47804 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1joPJQ-0004L0-DY for qemu-devel@archiver.kernel.org; Thu, 25 Jun 2020 06:40:56 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40334) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1joPIF-00038e-Ri for qemu-devel@nongnu.org; Thu, 25 Jun 2020 06:39:43 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:41058 helo=us-smtp-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 1joPIE-0003wQ-4g for qemu-devel@nongnu.org; Thu, 25 Jun 2020 06:39:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593081581; 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=NteMtL0MD3KIE074ggwyRQ3cXgmwcH4ws/J0fRIOSu8=; b=AHU94Y1SAeP24Hu9/Vm80KXfW/cR6ZZlSuZXfG7wVS4wLRjU9vg1pGcEf0NEELdLLDqa1/ f+cjxbzZk0Ps5ciIbh4+5Ii6AsTtPLUl0KrpQv5LnlRwQQVWNtnXKUgJEnsPfhoMQ94dX/ Drvk3Sh7cvxQFhjeWjATx5wzdFyca48= 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-332-HetRBGTjOqy8h0Dvmh9ryA-1; Thu, 25 Jun 2020 06:39:39 -0400 X-MC-Unique: HetRBGTjOqy8h0Dvmh9ryA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4FBF7107ACCA; Thu, 25 Jun 2020 10:39:38 +0000 (UTC) Received: from redhat.com (unknown [10.36.110.27]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 138A11010428; Thu, 25 Jun 2020 10:39:27 +0000 (UTC) Date: Thu, 25 Jun 2020 11:39:24 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Cornelia Huck Subject: Re: [RFC 0/4] Enable virtio-fs on s390x Message-ID: <20200625103924.GH1009994@redhat.com> References: <20200625100430.22407-1-mhartmay@linux.ibm.com> <20200625101935.GF1009994@redhat.com> <20200625123136.2c3c0ebe.cohuck@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200625123136.2c3c0ebe.cohuck@redhat.com> User-Agent: Mutt/1.14.0 (2020-05-02) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.120; envelope-from=berrange@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/25 00:45:15 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: "Michael S. Tsirkin" , qemu-devel@nongnu.org, Halil Pasic , Marc Hartmayer , Stefan Hajnoczi , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jun 25, 2020 at 12:31:36PM +0200, Cornelia Huck wrote: > On Thu, 25 Jun 2020 11:19:35 +0100 > Daniel P. Berrangé wrote: > > > On Thu, Jun 25, 2020 at 12:04:26PM +0200, Marc Hartmayer wrote: > > > This RFC is about enabling virtio-fs on s390x. For that we need > > > + some shim code (first patch), and we need > > > + libvhost-user to deal with virtio endiannes as mandated by the spec. > > > > > > The second part is trickier, because unlike QEMU we are not certain > > > about the guest's native endianness, which is needed to handle the > > > legacy-interface appropriately. In fact, this is the reason why just > > > RFC. > > > > > > One of the open questions is whether to build separate versions, one > > > for guest little endian and one for guest big endian, or do we want > > > something like a command line option? (Digression on the libvirt > > > modeling) > > > > When you talk about big vs little endian, are you referring to TCG > > scenarios with mixed host/guest arch, or arches which can support > > either endianess, or both ? i guess it doesn't matter actually, as > > I think the latter forces a specific answer. > > > > Considering that some architectures allow the guest OS to flip between > > big & little endian as they boot, libvirt cannot know what endianess > > the guest is using when it launches virtiofsd. It thus cannot pick > > between two different endianness builds of virtiofsd automatically. > > This would force the user to tell libvirt what arch the guest is using > > at the time they define the guest. This is an undesirable restriction > > for use cases where the admin of the guest OS has no direct control > > over the host config. > > Right, but that is in practice only a problem for legacy devices, isn't > it? The standard says that non-legacy devices use little-endian > everywhere; it's the legacy 'device endian' that is causing us > headaches. > > Which leads to the question: Do we really need to support legacy > virtio-fs devices, or can we just force virtio-1, as many (most?) newer > virtio devices do? I'd hope virtio-fs is already forced to modern only, as there's no legacy PCI ID assigned to it in the spec. 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 :|