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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 899DDC433F5 for ; Tue, 12 Oct 2021 06:49:02 +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 37F3D60187 for ; Tue, 12 Oct 2021 06:49:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 37F3D60187 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]:38116 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1maBav-0006DS-6L for qemu-devel@archiver.kernel.org; Tue, 12 Oct 2021 02:49:01 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35816) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1maBWw-0002kk-5h for qemu-devel@nongnu.org; Tue, 12 Oct 2021 02:44:54 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:48022) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1maBWu-0004Mu-F4 for qemu-devel@nongnu.org; Tue, 12 Oct 2021 02:44:53 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1634021091; 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=2vzpjSbfZeqWID4EtL0eqafpAXRwM5SISo3Qoc1dQSI=; b=WgN/qBFK9tO28m3wJ/h+5LHRpSI1d8a0+DvPcFGu08rfA30lagudwauvEnnCRq+WTt/LgQ TMwxpZSRVYXBnmk6SKgZFPC5mKQ7rb+P34vZDw/JubJEYVNb6RkiwZl7Kclefc46xnIADO U4YdmehPIOc/d9MtLZB8ZahovfOtQas= 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-497-RRKD2YyZPt-x2JpEeEiY0Q-1; Tue, 12 Oct 2021 02:44:50 -0400 X-MC-Unique: RRKD2YyZPt-x2JpEeEiY0Q-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A90CD835DE0; Tue, 12 Oct 2021 06:44:49 +0000 (UTC) Received: from sirius.home.kraxel.org (unknown [10.39.193.22]) by smtp.corp.redhat.com (Postfix) with ESMTPS id ED71960BF4; Tue, 12 Oct 2021 06:44:46 +0000 (UTC) Received: by sirius.home.kraxel.org (Postfix, from userid 1000) id 499BC1800393; Tue, 12 Oct 2021 08:44:45 +0200 (CEST) Date: Tue, 12 Oct 2021 08:44:45 +0200 From: Gerd Hoffmann To: "Michael S. Tsirkin" Subject: Re: [PATCH 6/6] pcie: expire pending delete Message-ID: <20211012064445.ur4ihnuaftzn76wc@sirius.home.kraxel.org> References: <20211011120504.254053-1-kraxel@redhat.com> <20211011120504.254053-7-kraxel@redhat.com> <20211011084310-mutt-send-email-mst@kernel.org> <20211012053034.faskn5y6b2hbbfys@sirius.home.kraxel.org> <20211012014515-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: <20211012014515-mutt-send-email-mst@kernel.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kraxel@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=kraxel@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.049, 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: Paolo Bonzini , Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= , qemu-devel@nongnu.org, Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Oct 12, 2021 at 01:46:35AM -0400, Michael S. Tsirkin wrote: > On Tue, Oct 12, 2021 at 07:30:34AM +0200, Gerd Hoffmann wrote: > > > > index f3ac04399969..477c8776aa27 100644 > > > > --- a/hw/pci/pcie.c > > > > +++ b/hw/pci/pcie.c > > > > @@ -549,6 +549,8 @@ void pcie_cap_slot_unplug_request_cb(HotplugHandler *hotplug_dev, > > > > } > > > > > > > > dev->pending_deleted_event = true; > > > > + dev->pending_deleted_expires_ms = > > > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + 5000; /* 5 secs */ > > > > > > > > /* In case user cancel the operation of multi-function hot-add, > > > > * remove the function that is unexposed to guest individually, > > > > > > > > > Well this will be barely enough, right? > > > > > > Once the Power > > > Indicator begins blinking, a 5-second abort interval exists during which a second depression of the > > > Attention Button cancels the operation. > > > > Well, canceling the hot-plug is not supported in qemu right now (there > > is no qmp command for that). I'm also not sure it makes sense in the > > first place for virtual machines. > > Yes. However if you resend an attention button press within the > 5 second window, guest will think you cancelled hot-plug > and act accordingly. > It's a fundamentally racy algorithm :( That's why re-sending an attention button press is blocked for 5 seconds. It's also blocked in case the guest blinks the power indicator (see patch #3). Both together work well in my testing, I can flood a (linux) guest with device_del commands without bad side effects: First device_del command sends attention button press. Then device_del is rejected because the 5 secs are not over yet. Then device_del is rejected because the indicator blinks. Then unplug completes (and qemu sends event). Then device_del fails because the device doesn't exist any more. take care, Gerd