From 25bd879ec16ad3b83a5b1c3f16faa55e696bfccb Mon Sep 17 00:00:00 2001 From: Mika Westerberg Date: Mon, 7 Jan 2019 16:09:40 +0300 Subject: [PATCH] PCI: pciehp: Assign ctrl->slot_ctrl before writing it to hardware 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 commit 720d6a671a6e ("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: 720d6a671a6e ("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 Signed-off-by: Mika Westerberg Signed-off-by: Bjorn Helgaas --- drivers/pci/hotplug/pciehp_hpc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index 7dd443a..cd9eae6 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -156,9 +156,9 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd, slot_ctrl |= (cmd & mask); ctrl->cmd_busy = 1; smp_mb(); + ctrl->slot_ctrl = slot_ctrl; pcie_capability_write_word(pdev, PCI_EXP_SLTCTL, slot_ctrl); ctrl->cmd_started = jiffies; - ctrl->slot_ctrl = slot_ctrl; /* * Controllers with the Intel CF118 and similar errata advertise -- 2.7.4