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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id CF11EC7619A for ; Wed, 5 Apr 2023 10:02:43 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pjzyS-0005Xy-7Q; Wed, 05 Apr 2023 06:02:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pjzyR-0005Xg-B0 for qemu-devel@nongnu.org; Wed, 05 Apr 2023 06:02:39 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pjzyP-0001SO-H8 for qemu-devel@nongnu.org; Wed, 05 Apr 2023 06:02:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1680688956; 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=fzroT10Iz8pTditWZ6zJs8YbKVhN6khiwPIsMlpaV9E=; b=Qg4tL1sOKoI/5e/SCTd5iOKRDoD0M4R+HBfsFJZGE2u14yHE3+isbvhrmT3Qm+8hsfl8HG 9h2UC75EHf8slqWKPq4Gy6npUWVwX/fhySQZFiSfYUwme8X0KgHkkh5I7RMrggej3iGN2X 0suOILa8mxhq0ni7MzOGm54GdFRJbbw= Received: from mail-lj1-f199.google.com (mail-lj1-f199.google.com [209.85.208.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-171-FG6OMGsOPau3ufH7KsBdtg-1; Wed, 05 Apr 2023 06:02:35 -0400 X-MC-Unique: FG6OMGsOPau3ufH7KsBdtg-1 Received: by mail-lj1-f199.google.com with SMTP id f16-20020a05651c03d000b0029bebfa766dso7732147ljp.11 for ; Wed, 05 Apr 2023 03:02:34 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680688953; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=fzroT10Iz8pTditWZ6zJs8YbKVhN6khiwPIsMlpaV9E=; b=0+kLym8nEpO5dtMnDq6Zfk9noWDn1VLxRZA8+JYxFr7fi9jsqxIjYecIsrGJw17qRs SzMyjYc7m9/ma2twvq1QeqKB/LdEEk9RuVSz/WGODKD3c24POded3BLddzRUlorK9Pl/ j7GJqQnDeCAeEdZKc3PciWpkaWx/Qg2XdEawS6RDLT7aODmDPY5zf3i+nrtr0N9yZoPO zGPfm02+ZFrvfIogBSHS51KKOgZ2PMHCVxyghwuwBG0CU8bfaz936CmCjH4aYAFMVHz+ o2XWTR4cMcmAhSySJK4t/J0xak6MuN2GsdudNGSRyTH43yFYZsNlRlkF7Qo6GkizR4vH 1FeA== X-Gm-Message-State: AAQBX9dFju7li/ZKtWfIGGdHvjeriQdEWaQX+XMgDcUeHTv0hrYQXoUt eUCWhyFjrdf1CPrSvKsaIueHDdPDpZG3YJJL/L9ipl4FhSkpKES9RmCTcGkT5VKBupBkloaPFij wO9w5e6gsARxkNDA= X-Received: by 2002:ac2:5eda:0:b0:4e8:221f:5886 with SMTP id d26-20020ac25eda000000b004e8221f5886mr1676570lfq.19.1680688953606; Wed, 05 Apr 2023 03:02:33 -0700 (PDT) X-Google-Smtp-Source: AKy350bbjfB6nA1Q7kOB/NgrrIWX6DEEKTfb0QBunxyX4Z/7HlJvVo2M/Lv6hwiGkHRJh7FYhvrw4g== X-Received: by 2002:ac2:5eda:0:b0:4e8:221f:5886 with SMTP id d26-20020ac25eda000000b004e8221f5886mr1676560lfq.19.1680688953205; Wed, 05 Apr 2023 03:02:33 -0700 (PDT) Received: from redhat.com ([2.52.139.22]) by smtp.gmail.com with ESMTPSA id i9-20020a50c3c9000000b005023a4b20dfsm7102513edf.2.2023.04.05.03.02.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Apr 2023 03:02:32 -0700 (PDT) Date: Wed, 5 Apr 2023 06:02:29 -0400 From: "Michael S. Tsirkin" To: Igor Mammedov Cc: qemu-devel@nongnu.org, anisinha@redhat.com, jusual@redhat.com, kraxel@redhat.com Subject: Re: [PATCH v2] acpi: pcihp: make pending delete blocking action expire Message-ID: <20230405055946-mutt-send-email-mst@kernel.org> References: <20230405083444.1536720-1-imammedo@redhat.com> <20230405044231-mutt-send-email-mst@kernel.org> <20230405113856.72065fd0@imammedo.users.ipa.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230405113856.72065fd0@imammedo.users.ipa.redhat.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com 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_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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Apr 05, 2023 at 11:38:56AM +0200, Igor Mammedov wrote: > On Wed, 5 Apr 2023 04:47:48 -0400 > "Michael S. Tsirkin" wrote: > > > On Wed, Apr 05, 2023 at 10:34:44AM +0200, Igor Mammedov wrote: > > > with Q35 using ACPI PCI hotplug by default, user's request to unplug > > > device is ignored when it's issued before guest OS has been booted. > > > And any additional attempt to request device hot-unplug afterwards > > > results in following error: > > > > > > "Device XYZ is already in the process of unplug" > > > > > > arguably it can be considered as a regression introduced by [2], > > > before which it was possible to issue unplug request multiple > > > times. > > > > > > Allowing pending delete blocking expire brings ACPI PCI hotplug > > > on par with native PCIe unplug behavior [1] and allows user > > > to repeat unplug requests at propper times. > > > Set expire timeout to arbitrary 1msec so user won't be able to > > > flood guest with SCI interrupts by calling device_del in tight loop. > > > > > > PS: > > > ACPI spec doesn't mandate what OSPM can do with GPEx.status > > > bits set before it's booted => it's impl. depended. > > > Status bits may be retained (I tested with one Windows version) > > > or cleared (Linux since 2.6 kernel times) during guest's ACPI > > > subsystem initialization. > > > Clearing status bits (though not wrong per se) hides the unplug > > > event from guest, and it's upto user to repeat device_del later > > > when guest is able to handle unplug requests. > > > > > > 1) 18416c62e3 ("pcie: expire pending delete") > > > 2) > > > Fixes: cce8944cc9ef ("qdev-monitor: Forbid repeated device_del") > > > Signed-off-by: Igor Mammedov > > > > I feel a real solution is to detect guest handling the > > event such as clearing GPE and allowing resending > > the interrupt then. > > I did consider preserving(masking clearing attempt) of GPE0.sts[] > IF en[] hasn't been enabled ever (i.e. should help with unplug at > the 1st boot). But that won't work across reboots (depends on > reboot kind) and it's twisting rules wrt spec (platform(QEMU/fw) > may set status bits, but it's upto OSPM to decide what to do with > them (when and how clear or ignore them). > > > A similar strategy should be possible with the attention > > button. > > > > > This patch is more of a band-aid - it is possible that guest > > rebooted and so user knows a new device_del is required, > > and we arbitrarily reject that. Right? > You lost me here. Can you elaborate? I request device deletion but guest was rebooting losing state. I want to request deletion again but the request will fail until 1ms passes. 1ms is not a lot but I really don't want management to learn weird tricks like waiting for 1ms. > > > > This is arguably a regression but not in this release yes? > > So I don't think it needs to block qemu release. > > > > > > > --- > > > v2: > > > * change timeout to 1ms > > > * add comment to expire usage > > > * massage commit message to be a bit more clear > > > > > > CC: mst@redhat.com > > > CC: anisinha@redhat.com > > > CC: jusual@redhat.com > > > CC: kraxel@redhat.com > > > > It's helpful to have CC before --- so backporters know whom to CC, too. > > ok, I'll fix it up and respin > > > > > > --- > > > hw/acpi/pcihp.c | 10 ++++++++++ > > > 1 file changed, 10 insertions(+) > > > > > > diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c > > > index dcfb779a7a..5daa732a33 100644 > > > --- a/hw/acpi/pcihp.c > > > +++ b/hw/acpi/pcihp.c > > > @@ -357,6 +357,16 @@ void acpi_pcihp_device_unplug_request_cb(HotplugHandler *hotplug_dev, > > > * acpi_pcihp_eject_slot() when the operation is completed. > > > */ > > > pdev->qdev.pending_deleted_event = true; > > > + /* if unplug was requested before OSPM is initialized, > > > + * linux kernel will clear GPE0.sts[] bits during boot, which effectively > > > + * hides unplug event. BAnd than followup qmp_device_del() calls remain > > > > BAnd? > > > > > + * blocked by above flag permanently. > > > + * Unblock qmp_device_del() by setting expire limit, so user can > > > + * repeat unplug request later when OSPM has been booted. > > > + */ > > > + pdev->qdev.pending_deleted_expires_ms = > > > + qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL); /* 1 msec */ > > > + > > > s->acpi_pcihp_pci_status[bsel].down |= (1U << slot); > > > acpi_send_event(DEVICE(hotplug_dev), ACPI_PCI_HOTPLUG_STATUS); > > > } > > > -- > > > 2.39.1 > >