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=-3.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 3066BC388F9 for ; Tue, 27 Oct 2020 13:03:01 +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 A353920773 for ; Tue, 27 Oct 2020 13:03:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="iZgJrwyF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A353920773 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]:52302 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kXOct-0002fG-DF for qemu-devel@archiver.kernel.org; Tue, 27 Oct 2020 09:02:59 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43410) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kXOVK-00033d-88 for qemu-devel@nongnu.org; Tue, 27 Oct 2020 08:55:10 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:59987) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kXOVF-0001MW-Kp for qemu-devel@nongnu.org; Tue, 27 Oct 2020 08:55:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603803278; 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=NI696C0arYXyJKNdzV6AT0qwIrcLWRp7/iEfe09jum4=; b=iZgJrwyFTt4ARP76AR7d7bw3mAuWWbEIchZjcEcp0VdediHGd5idv/+kEbtLGEpfgu1/0g gvT0TqZYHBlWbco+0W4SVldcQond2eUnpbwbDtDGTW0SVNbA957O7b9+MhXR4BAlDkZGqC IdcxfdG+8Fn/9jCC00tuc9lEpPqLH/U= 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-479-W4tvVg4pN5OKUxqp3C9ccQ-1; Tue, 27 Oct 2020 08:54:36 -0400 X-MC-Unique: W4tvVg4pN5OKUxqp3C9ccQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 15C29802B77 for ; Tue, 27 Oct 2020 12:54:35 +0000 (UTC) Received: from localhost (unknown [10.40.208.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1969F55760; Tue, 27 Oct 2020 12:54:28 +0000 (UTC) Date: Tue, 27 Oct 2020 13:54:26 +0100 From: Igor Mammedov To: "Michael S. Tsirkin" Subject: Re: [PATCH] pci: Refuse to hotplug PCI Devices when the Guest OS is not ready Message-ID: <20201027135426.765dd19b@redhat.com> In-Reply-To: <20201027072430-mutt-send-email-mst@kernel.org> References: <20201022080354-mutt-send-email-mst@kernel.org> <20201022235632.7f69ddc9@yekko.fritz.box> <20201022100028-mutt-send-email-mst@kernel.org> <20201022102857-mutt-send-email-mst@kernel.org> <20201022110016-mutt-send-email-mst@kernel.org> <20201026174537.128a4173@yekko.fritz.box> <20201027072430-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=imammedo@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=216.205.24.124; envelope-from=imammedo@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/27 01:06:06 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H4=0.001, RCVD_IN_MSPIKE_WL=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: David Gibson , Julia Suvorova , qemu devel list Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 27 Oct 2020 07:26:44 -0400 "Michael S. Tsirkin" wrote: > On Mon, Oct 26, 2020 at 05:45:37PM +1100, David Gibson wrote: > > On Fri, 23 Oct 2020 09:26:48 +0300 > > Marcel Apfelbaum wrote: > > > > > Hi Michael, > > > > > > On Thu, Oct 22, 2020 at 6:01 PM Michael S. Tsirkin wrote: > > > > > > [...] [...] > > > Simplistic does not mean wrong or incorrect. > > > I fail to see why it is not enough. > > > > > > What QEMU can do better? Wait an unbounded time for the blinking to finish? > > > > It certainly shouldn't wait an unbounded time. But a wait with timeout > > seems worth investigating to me. racy, timeout is bound to break once it's in overcommited env. > If it's helpful, I'd add a query to check state > so management can figure out why doesn't guest see device yet. that means mgmt would have to poll it and forward it to user somehow. > But otherwise just buffer the request until such time as > we can deliver it to guest ... I have more questions wrt the suggestion/workflow: * at what place would you suggest buffering it? * what would be the request in this case, i.e. create PCI device anyways and try to signal hotplug event later? * what would baremethal do in such case? * what to do in case guest is never ready, what user should do in such case? * can be such device be removed? not sure that all of this is worth of the effort and added complexity. alternatively: maybe ports can send QMP events about it's state changes, which end user would be able to see + error like in this patch. On top of it, mgmt could build a better UIx, like retry/notify logic if that's what user really wishes for and configures (it would be up to user to define behaviour). > > > What if we have a buggy guest with a kernel stuck in blinking? > > > Is QEMU's responsibility to emulate the operator itself? Because the > > > operator > > > is the one who is supposed to wait. > > > > > > > > > Thanks, > > > Marcel > > > > > > [...] > > > > > > -- > > David Gibson > > Principal Software Engineer, Virtualization, Red Hat > > >