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=-3.5 required=3.0 tests=BAYES_00,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 0EDE2C4338F for ; Mon, 23 Aug 2021 21:57:39 +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 9AB58611CB for ; Mon, 23 Aug 2021 21:57:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 9AB58611CB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:50498 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mIHwn-0006Cr-TK for qemu-devel@archiver.kernel.org; Mon, 23 Aug 2021 17:57:37 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34518) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mIHwF-0005YT-JT for qemu-devel@nongnu.org; Mon, 23 Aug 2021 17:57:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:56131) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mIHwE-0002ux-2l for qemu-devel@nongnu.org; Mon, 23 Aug 2021 17:57:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629755821; 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: in-reply-to:in-reply-to:references:references; bh=NUMDRcpQBFc9zVlWLALkhn88+VbIC6BLOhglU+lFK5A=; b=GoKfxsprlE8xa/BvJSWlipq5ezXArW+t3Fr7uzI5sqPApCQMhJuS/7pamCIofHMum8payk TiRV+JmOG8hRtelYu3roe9UgBMRFQQmhJN9Vjis6sMMv1lIeuciWnQvett9qJPnCFmRoiD 9S7eLJ3lwM9xcOm3W73zrd5RKqlVCd0= 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-220-9039II9tMfOsIggoeBA1kg-1; Mon, 23 Aug 2021 17:56:59 -0400 X-MC-Unique: 9039II9tMfOsIggoeBA1kg-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 2AC3E8799EC for ; Mon, 23 Aug 2021 21:56:59 +0000 (UTC) Received: from localhost (unknown [10.22.32.130]) by smtp.corp.redhat.com (Postfix) with ESMTP id CC55A60854; Mon, 23 Aug 2021 21:56:23 +0000 (UTC) Date: Mon, 23 Aug 2021 17:56:23 -0400 From: Eduardo Habkost To: Peter Xu Subject: Re: [PATCH 4/4] vl: Prioritize realizations of devices Message-ID: <20210823215623.bagyo3oojdpk3byj@habkost.net> References: <20210818194217.110451-1-peterx@redhat.com> <20210818194318.110993-1-peterx@redhat.com> <20210823184912.mazqfn7gurntj7ld@habkost.net> <20210823210703.cikdkhvyeqqypaqa@habkost.net> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ehabkost@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=ehabkost@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.743, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel P =?utf-8?B?LiBCZXJyYW5nw6k=?= , "Michael S . Tsirkin" , Jason Wang , qemu-devel@nongnu.org, Markus Armbruster , Eric Auger , Alex Williamson , Paolo Bonzini , "Dr . David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Aug 23, 2021 at 05:31:46PM -0400, Peter Xu wrote: > On Mon, Aug 23, 2021 at 05:07:03PM -0400, Eduardo Habkost wrote: > > To give just one example: > > > > $ (echo 'info pci';echo quit;) | qemu-system-x86_64 -device virtio-net-pci -device e1000e -monitor stdio | tail -n 20 > > Bus 0, device 4, function 0: > > Ethernet controller: PCI device 1af4:1000 > > PCI subsystem 1af4:0001 > > IRQ 0, pin A > > BAR0: I/O at 0xffffffffffffffff [0x001e]. > > BAR1: 32 bit memory at 0xffffffffffffffff [0x00000ffe]. > > BAR4: 64 bit prefetchable memory at 0xffffffffffffffff [0x00003ffe]. > > BAR6: 32 bit memory at 0xffffffffffffffff [0x0003fffe]. > > id "" > > Bus 0, device 5, function 0: > > Ethernet controller: PCI device 8086:10d3 > > PCI subsystem 8086:0000 > > IRQ 0, pin A > > BAR0: 32 bit memory at 0xffffffffffffffff [0x0001fffe]. > > BAR1: 32 bit memory at 0xffffffffffffffff [0x0001fffe]. > > BAR2: I/O at 0xffffffffffffffff [0x001e]. > > BAR3: 32 bit memory at 0xffffffffffffffff [0x00003ffe]. > > BAR6: 32 bit memory at 0xffffffffffffffff [0x0003fffe]. > > id "" > > (qemu) quit > > $ (echo 'info pci';echo quit;) | qemu-system-x86_64 -device e1000e -device virtio-net-pci -monitor stdio | tail -n 20 > > Bus 0, device 4, function 0: > > Ethernet controller: PCI device 8086:10d3 > > PCI subsystem 8086:0000 > > IRQ 0, pin A > > BAR0: 32 bit memory at 0xffffffffffffffff [0x0001fffe]. > > BAR1: 32 bit memory at 0xffffffffffffffff [0x0001fffe]. > > BAR2: I/O at 0xffffffffffffffff [0x001e]. > > BAR3: 32 bit memory at 0xffffffffffffffff [0x00003ffe]. > > BAR6: 32 bit memory at 0xffffffffffffffff [0x0003fffe]. > > id "" > > Bus 0, device 5, function 0: > > Ethernet controller: PCI device 1af4:1000 > > PCI subsystem 1af4:0001 > > IRQ 0, pin A > > BAR0: I/O at 0xffffffffffffffff [0x001e]. > > BAR1: 32 bit memory at 0xffffffffffffffff [0x00000ffe]. > > BAR4: 64 bit prefetchable memory at 0xffffffffffffffff [0x00003ffe]. > > BAR6: 32 bit memory at 0xffffffffffffffff [0x0003fffe]. > > id "" > > (qemu) quit > > > > > > If the order of the -device arguments changes, the devices are assigned to > > different PCI slots. > > Thanks for the example. > > Initially I thought about this and didn't think it an issue (because serious > users will always specify addr=XXX for -device; I thought libvirt always does > that), but I do remember that guest OS could identify its hardware config with > devfn number, so nmcli may mess up its config with before/after this change > indeed.. > > I can use a custom sort to replace qsort() to guarantee that. > > Do you have other examples in mind that I may have overlooked, especially I may > not be able to fix by a custom sort with only moving priority>=1 devices? I don't have any other example, but I assume address assignment based on ordering is a common pattern in device code. I would take a very close and careful look at the devices with non-default vmsd priority. If you can prove that the 13 device types with non-default priority are all order-insensitive, a custom sort function as you describe might be safe. -- Eduardo