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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id h23-20020a170906261700b008e0bb004976sm7083995ejc.134.2023.04.05.02.38.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Apr 2023 02:38:57 -0700 (PDT) Date: Wed, 5 Apr 2023 11:38:56 +0200 From: Igor Mammedov To: "Michael S. Tsirkin" 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: <20230405113856.72065fd0@imammedo.users.ipa.redhat.com> In-Reply-To: <20230405044231-mutt-send-email-mst@kernel.org> References: <20230405083444.1536720-1-imammedo@redhat.com> <20230405044231-mutt-send-email-mst@kernel.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.37; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=imammedo@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, 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? > > 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 >