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=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 EB68BC433DF for ; Thu, 2 Jul 2020 11:57:48 +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 B702C20737 for ; Thu, 2 Jul 2020 11:57:48 +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="f3D9XMjj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B702C20737 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]:53740 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jqxqe-0002HP-0O for qemu-devel@archiver.kernel.org; Thu, 02 Jul 2020 07:57:48 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:37288) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jqxpH-0000x5-OU for qemu-devel@nongnu.org; Thu, 02 Jul 2020 07:56:23 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:33981 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 1jqxpF-0000Tc-9Z for qemu-devel@nongnu.org; Thu, 02 Jul 2020 07:56:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593690980; 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=9Uin6movxwMyc8XgyNMZtlyl7XU7RB8ySe0FH5bhRhQ=; b=f3D9XMjjzhUZGq87ie2gZ0nPFZXV9B6XApPMM0pJOoUXSEJqi2xg06BHvL/5A+kJpxUozS WgWlhGFEK+ososSBJNKZm681wxaAzP9zNIgEO+8aEetLOfFUVWbyY7aUQc5OAXBA220QeP o1FBOLP+j/jlE/sSMUfFwr1Lj0xbhek= 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-89-uhb7YWDxNfirNMfgVQMgrw-1; Thu, 02 Jul 2020 07:56:18 -0400 X-MC-Unique: uhb7YWDxNfirNMfgVQMgrw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8C138BFC2 for ; Thu, 2 Jul 2020 11:56:17 +0000 (UTC) Received: from gondolin (ovpn-113-54.ams2.redhat.com [10.36.113.54]) by smtp.corp.redhat.com (Postfix) with ESMTP id A67FB79227; Thu, 2 Jul 2020 11:56:10 +0000 (UTC) Date: Thu, 2 Jul 2020 13:55:59 +0200 From: Cornelia Huck To: "Michael S. Tsirkin" Subject: Re: [PATCH RFC] virtio-fs: force virtio 1.x usage Message-ID: <20200702135559.761fb165.cohuck@redhat.com> In-Reply-To: <20200702071627-mutt-send-email-mst@kernel.org> References: <20200629102758.421552-1-cohuck@redhat.com> <20200630121037.GC91444@stefanha-x1.localdomain> <20200630142504.688aa989.cohuck@redhat.com> <20200630090327-mutt-send-email-mst@kernel.org> <20200701181917.62538421.cohuck@redhat.com> <20200702060555-mutt-send-email-mst@kernel.org> <20200702124538.0ba5d334.cohuck@redhat.com> <20200702071627-mutt-send-email-mst@kernel.org> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=cohuck@redhat.com 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=207.211.31.120; envelope-from=cohuck@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/02 03:23:40 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 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: , Cc: "Dr. David Alan Gilbert" , Stefan Hajnoczi , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, 2 Jul 2020 07:22:49 -0400 "Michael S. Tsirkin" wrote: > On Thu, Jul 02, 2020 at 12:45:38PM +0200, Cornelia Huck wrote: > > On Thu, 2 Jul 2020 06:16:06 -0400 > > "Michael S. Tsirkin" wrote: > > > > > On Wed, Jul 01, 2020 at 06:19:17PM +0200, Cornelia Huck wrote: > > > > On Tue, 30 Jun 2020 09:04:38 -0400 > > > > "Michael S. Tsirkin" wrote: > > > > > > > > > On Tue, Jun 30, 2020 at 02:25:04PM +0200, Cornelia Huck wrote: > > > > > > > > > > What bothers me most is that you need to explicitly request a device to > > > > > > be modern-only, while that should be the default for any newly added > > > > > > device. Hence the approach with the centralized list of device types > > > > > > mentioned in a parallel thread. The main problem with that is that the > > > > > > proxy device starts getting realized before the virtio device with its > > > > > > id is present... I failed to find a solution so far. But I'd really > > > > > > like an approach that can work for all transports. > > > > > > > > > > So how about simply validating that the device is modern only, > > > > > unless it's one of the whitelist? > > > > > > > > Who would do the validation, the virtio core? How can it distinguish > > > > between transitional and non-transitional? But maybe I'm just not > > > > getting your idea. > > > > > > OK I've been thinking about two ideas, we can use them both: > > > 1. virtio core: that can detect VIRTIO_1 being clear > > > in virtio_validate_features. > > > > After feature negotiation is complete? That feels like a regression in > > behaviour: You would be able to add a device that may not be usable > > (and you'll only find out after the guest tried to use it), instead of > > making sure that only a non-transitional device can be added to start > > with. > > I mean, we can still have transports validate, that is point 2. > It seems prudent to check though, since guest could be buggy > ignoring bits that it got. > > > (We do not validate if the guest did not negotiate VERSION_1, but we > > can certainly add a special case for the "guest did not accept offered > > VERSION_1" case.) > > exaclty. > > > > > > 2. transports: could use a core API to detect whether > > > device can be a legacy one, to block device creation. > > > > That would be the best, but how do we get around the "transport does > > not know the device type until it is too late" problem? Unless you want > > to redo the internal interfaces. > > Oh. I think I am missing something. > So I'm considering virtio_pci_device_plugged for example. > > > static void virtio_pci_device_plugged(DeviceState *d, Error **errp) > { > VirtIOPCIProxy *proxy = VIRTIO_PCI(d); > VirtioBusState *bus = &proxy->bus; > bool legacy = virtio_pci_legacy(proxy); > bool modern; > bool modern_pio = proxy->flags & VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY; > uint8_t *config; > uint32_t size; > VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus); > > /* > > .. > > } > > can't we check device type here and make sure it matches the "legacy" > flag? It would be a change in behaviour: Currently, I can specify e.g. -device virtio-gpu-pci,disable-legacy=off,disable-modern=true and the code in the realize function would force it to a modern-only device. Checking in the plugged function would cause it to fail. This might be preferable, but could break existing command lines. Note that ccw is different: if I specify -device virtio-gpu-ccw,max_revision=0 it actually fails with qemu-system-s390x: -device virtio-gpu-ccw,max_revision=0: Invalid value of property max_rev (is 0 expected >= 1) so moving to the plugged function would not cause a change in behaviour from the user's point of view. > > > > > > > > > > > > > Also, ccw does not currently have a way to explicitly configure a > > > > device non-transitional; the revisions can be used to fence off newer > > > > features, going down to legacy-only, but fencing off older features is > > > > not possible (that is only done by the device, if it has no legacy > > > > support). > > > > > > I guess for ccw only option 1 works. > > > > > > > Or keep it as-is, and disallow legacy for the individual device types, > > with the validate check as a safety net during development. > > Problem is people cut and paste from transitional devices. That should not be a problem for ccw (as transitional and non-transitional are the same on the command line); moreover, people are unlikely to set max_revision themselves (this is usually only done by compat machines). If changing the behaviour for pci is acceptable, we can sure move to the plugged approach.