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Shameerali reported that running v4.20-rc1 as QEMU guest, the PCIe hotplug port times out during boot: pciehp 0000:00:01.0:pcie004: Timeout on hotplug command 0x03f1 (issued 1016 msec ago) pciehp 0000:00:01.0:pcie004: Timeout on hotplug command 0x03f1 (issued 1024 msec ago) pciehp 0000:00:01.0:pcie004: Failed to check link status pciehp 0000:00:01.0:pcie004: Timeout on hotplug command 0x02f1 (issued 2520 msec ago) The issue was bisected down to commit720d6a671a("PCI: pciehp: Do not handle events if interrupts are masked") and was further analyzed by the reporter to be caused by the fact that pciehp first updates the hardware and only then cache the ctrl->slot_ctrl in pcie_do_write_cmd(). If the interrupt happens before we cache the value, pciehp_isr() reads value 0 and decides that the interrupt was not meant for it causing the above timeout to trigger. Fix by moving ctrl->slot_ctrl assignment to happen before it is written to the hardware. Fixes:720d6a671a("PCI: pciehp: Do not handle events if interrupts are masked") Link: https://lore.kernel.org/linux-pci/5FC3163CFD30C246ABAA99954A238FA8387DD344@FRAEML521-MBX.china.huawei.com Reported-by: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.