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[2.214.14.217]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4887a30bcc4sm22563923f8f.1.2026.09.27.10.52.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 27 Sep 2026 10:52:13 -0700 (PDT) From: Abhin Parekadan Jose To: Bjorn Helgaas , Lukas Wunner , "Michael S. Tsirkin" Cc: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , Shuai Xue , Kees Cook , Mahesh J Salgaonkar , Oliver O'Halloran , linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Abhin Parekadan Jose Subject: [PATCH RFC v3 4/5] PCI: pciehp: Report surprise removal from pciehp_isr() Date: Sun, 27 Sep 2026 17:52:01 +0000 Message-ID: <20260927175203.928270-5-abhinjoses@gmail.com> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20260927175203.928270-1-abhinjoses@gmail.com> References: <20260927175203.928270-1-abhinjoses@gmail.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A surprise removal during a safe removal cannot be reported: the removal blocks waiting on a device interrupt or status read, and the single-threaded IRQ thread is itself executing that removal, so it cannot report that the device is gone. The removal hangs. The hardirq handler pciehp_isr() still runs while the IRQ thread is blocked, so it can report the disconnect. However, pciehp_ist() deliberately ignores link and presence changes caused by a Secondary Bus Reset or Downstream Port Containment, where the device is only temporarily inaccessible. Distinguishing those normally requires waiting for the SBR or DPC to conclude, which takes seconds and is not possible in hardirq context. Schedule a work item from pciehp_isr() when a PDC or DLLSC event arrives and neither Presence Detect State nor Data Link Layer Link Active indicates that a card is present. This provides us a pathway to wait/block/sleep as we will not be in pciehp_isr(). In pciehp_disconnect_work(), wait for the DPC recovery or SBR to complete before checking presence and not consume the link change flags, so that pciehp_ist() can still see them and ignore the link change if it was caused by a DPC or SBR. Even after the DPC or SBR has completed, if the device is really gone then pciehp_disconnect_work() will see that and report the surprise removal. Like pciehp_ist(), it holds a runtime PM reference on the port and checks presence under reset_lock, since a slot reset may make Presence Detect State and Link Active flap. Link: https://lore.kernel.org/all/aHlZE18kPuHuDtTT@wunner.de/ Signed-off-by: Abhin Parekadan Jose Assisted-by: LLM --- Changes since RFC v1: - Drop schedule_notification_work(). pci_dev_set_disconnected() schedules the driver's disconnect_work again, as in patch 1, for all callers, and pciehp_disconnect_work() calls it through pci_walk_bus(). (Michael) - Return early from pciehp_disconnect_work() if pending_events is zero. pciehp_ist() has then already taken the events and handles them itself. (Sashiko) - Treat a read error of the presence check as "not present", both when scheduling the work in pciehp_isr() and when checking presence in pciehp_disconnect_work(). (Sashiko) - Check presence with pciehp_card_present_or_link_active(), as pciehp_ist() does, so that a port with Presence Detect State hardwired to zero is not mistaken for an empty slot. - In pciehp_isr(), check presence before dropping the runtime PM reference on the port's parent. In pciehp_disconnect_work(), take a runtime PM reference and check presence under reset_lock. - Don't call the spurious link change test from pciehp_disconnect_work(). It consumes the one-shot flags PCI_DPC_RECOVERED and PCI_LINK_CHANGED, so pciehp_ist() could miss them and tear down a device that was only reset. Await DPC recovery and Secondary Bus Reset with the new pci_dpc_wait_recovery() and pci_hp_wait_link_change() (patches 2 and 3) instead, without consuming the flags. pciehp_is_spurious_link_change() is dropped and pciehp_ist() is unchanged. (Sashiko) RFC v1: https://lore.kernel.org/all/20260905183905.997833-3-abhinjoses@gmail.com/ Michael's review: https://lore.kernel.org/all/20260912115420-mutt-send-email-mst@kernel.org/ Sashiko review: https://lore.kernel.org/all/20260905185217.E9BC21F00A3A@smtp.kernel.org/ --- drivers/pci/hotplug/pciehp.h | 1 + drivers/pci/hotplug/pciehp_hpc.c | 67 ++++++++++++++++++++++++++++++++ 2 files changed, 68 insertions(+) diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h index debc79b0adfb2..c8ceb9320e2e9 100644 --- a/drivers/pci/hotplug/pciehp.h +++ b/drivers/pci/hotplug/pciehp.h @@ -116,6 +116,7 @@ struct controller { unsigned int ist_running; int request_result; wait_queue_head_t requester; + struct work_struct disconnect_work; }; /** diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index 4c62140a3cb44..470cc16d4a828 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -620,12 +620,64 @@ static void pciehp_ignore_link_change(struct controller *ctrl, up_read(&ctrl->reset_lock); } +/* + * Workaround to not wait in the isr. + */ +static void pciehp_disconnect_work(struct work_struct *work) +{ + struct pci_bus *bus; + struct controller *ctrl = container_of(work, struct controller, + disconnect_work); + struct pci_dev *pdev = ctrl_dev(ctrl); + u32 events; + int present; + + events = atomic_read(&ctrl->pending_events); + + /* + * Zero means pciehp_ist() has already consumed the events with + * atomic_xchg() and is handling them itself, with the full event + * mask available for the spurious link change test. Leave it to + * the IRQ thread: acting here would override its decision, and a + * zero carries no information about the device. + * + * The events only stay pending for us when the IRQ thread is + * blocked and cannot drain them, e.g. in pciehp_unconfigure_device() + * during a safe removal. That is the case this work item exists + * for. + */ + if (!events) + return; + + pci_config_pm_runtime_get(pdev); + + /* Wait for DPC recovery or a SBR to complete */ + pci_dpc_wait_recovery(pdev); + pci_hp_wait_link_change(pdev); + + /* Presence Detect State and Link Active may flap during a slot reset */ + down_read_nested(&ctrl->reset_lock, ctrl->depth); + present = pciehp_card_present_or_link_active(ctrl); + up_read(&ctrl->reset_lock); + + pci_config_pm_runtime_put(pdev); + + bus = ctrl->pcie->port->subordinate; + + /* The card may have returned */ + if (!bus || present > 0) + return; + + pci_walk_bus(bus, pci_dev_set_disconnected, NULL); +} + static irqreturn_t pciehp_isr(int irq, void *dev_id) { struct controller *ctrl = (struct controller *)dev_id; struct pci_dev *pdev = ctrl_dev(ctrl); struct device *parent = pdev->dev.parent; u16 status, events = 0; + int present = 1; /* * Interrupts only occur in D3hot or shallower and only if enabled @@ -697,6 +749,14 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id) } ctrl_dbg(ctrl, "pending interrupts %#06x from Slot Status\n", events); + + /* + * Check presence while the port is kept accessible. This may race + * with a slot reset, so pciehp_disconnect_work() checks again. + */ + if (events & (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC)) + present = pciehp_card_present_or_link_active(ctrl); + if (parent) pm_runtime_put(parent); @@ -722,6 +782,11 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id) /* Save pending events for consumption by IRQ thread. */ atomic_or(events, &ctrl->pending_events); + + /* The card may be gone, let process context decide */ + if (present <= 0) + schedule_work(&ctrl->disconnect_work); + return IRQ_WAKE_THREAD; } @@ -1036,6 +1101,7 @@ struct controller *pcie_init(struct pcie_device *dev) init_waitqueue_head(&ctrl->requester); init_waitqueue_head(&ctrl->queue); INIT_DELAYED_WORK(&ctrl->button_work, pciehp_queue_pushbutton_work); + INIT_WORK(&ctrl->disconnect_work, pciehp_disconnect_work); dbg_ctrl(ctrl); down_read(&pci_bus_sem); @@ -1096,6 +1162,7 @@ struct controller *pcie_init(struct pcie_device *dev) void pciehp_release_ctrl(struct controller *ctrl) { cancel_delayed_work_sync(&ctrl->button_work); + cancel_work_sync(&ctrl->disconnect_work); kfree(ctrl); } -- 2.51.1