This is a note to let you know that I've just added the patch titled PCI: pciehp: Fix infinite loop in IRQ handler upon power fault to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: pci-pciehp-fix-infinite-loop-in-irq-handler-upon-power-fault.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 23584c1ed3e15a6f4bfab8dc5a88d94ab929ee12 Mon Sep 17 00:00:00 2001 From: Lukas Wunner <lukas@xxxxxxxxx> Date: Wed, 17 Nov 2021 23:22:09 +0100 Subject: PCI: pciehp: Fix infinite loop in IRQ handler upon power fault From: Lukas Wunner <lukas@xxxxxxxxx> commit 23584c1ed3e15a6f4bfab8dc5a88d94ab929ee12 upstream. The Power Fault Detected bit in the Slot Status register differs from all other hotplug events in that it is sticky: It can only be cleared after turning off slot power. Per PCIe r5.0, sec. 6.7.1.8: If a power controller detects a main power fault on the hot-plug slot, it must automatically set its internal main power fault latch [...]. The main power fault latch is cleared when software turns off power to the hot-plug slot. The stickiness used to cause interrupt storms and infinite loops which were fixed in 2009 by commits 5651c48cfafe ("PCI pciehp: fix power fault interrupt storm problem") and 99f0169c17f3 ("PCI: pciehp: enable software notification on empty slots"). Unfortunately in 2020 the infinite loop issue was inadvertently reintroduced by commit 8edf5332c393 ("PCI: pciehp: Fix MSI interrupt race"): The hardirq handler pciehp_isr() clears the PFD bit until pciehp's power_fault_detected flag is set. That happens in the IRQ thread pciehp_ist(), which never learns of the event because the hardirq handler is stuck in an infinite loop. Fix by setting the power_fault_detected flag already in the hardirq handler. Link: https://bugzilla.kernel.org/show_bug.cgi?id=214989 Link: https://lore.kernel.org/linux-pci/DM8PR11MB5702255A6A92F735D90A4446868B9@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 8edf5332c393 ("PCI: pciehp: Fix MSI interrupt race") Link: https://lore.kernel.org/r/66eaeef31d4997ceea357ad93259f290ededecfd.1637187226.git.lukas@xxxxxxxxx Reported-by: Joseph Bao <joseph.bao@xxxxxxxxx> Tested-by: Joseph Bao <joseph.bao@xxxxxxxxx> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx # v4.19+ Cc: Stuart Hayes <stuart.w.hayes@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/pci/hotplug/pciehp_hpc.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -642,6 +642,8 @@ read_status: */ if (ctrl->power_fault_detected) status &= ~PCI_EXP_SLTSTA_PFD; + else if (status & PCI_EXP_SLTSTA_PFD) + ctrl->power_fault_detected = true; events |= status; if (!events) { @@ -651,7 +653,7 @@ read_status: } if (status) { - pcie_capability_write_word(pdev, PCI_EXP_SLTSTA, events); + pcie_capability_write_word(pdev, PCI_EXP_SLTSTA, status); /* * In MSI mode, all event bits must be zero before the port @@ -725,8 +727,7 @@ static irqreturn_t pciehp_ist(int irq, v } /* Check Power Fault Detected */ - if ((events & PCI_EXP_SLTSTA_PFD) && !ctrl->power_fault_detected) { - ctrl->power_fault_detected = 1; + if (events & PCI_EXP_SLTSTA_PFD) { ctrl_err(ctrl, "Slot(%s): Power fault\n", slot_name(ctrl)); pciehp_set_indicators(ctrl, PCI_EXP_SLTCTL_PWR_IND_OFF, PCI_EXP_SLTCTL_ATTN_IND_ON); Patches currently in stable-queue which might be from lukas@xxxxxxxxx are queue-5.15/pci-pciehp-fix-infinite-loop-in-irq-handler-upon-power-fault.patch queue-5.15/serial-fix-incorrect-rs485-polarity-on-uart-open.patch queue-5.15/serial-pl011-drop-cr-register-reset-on-set_termios.patch queue-5.15/serial-core-keep-mctrl-register-state-and-cached-cop.patch queue-5.15/serial-pl010-drop-cr-register-reset-on-set_termios.patch queue-5.15/pci-pciehp-use-down_read-write_nested-reset_lock-to-fix-lockdep-errors.patch