On Mon, Jan 24, 2022 at 07:44:04PM +0100, Greg Kroah-Hartman wrote: > From: Lukas Wunner <lukas@xxxxxxxxx> > > commit 23584c1ed3e15a6f4bfab8dc5a88d94ab929ee12 upstream. I would hold off on backporting the pciehp changes until we resolve this regression in v5.17-rc1: https://bugzilla.kernel.org/show_bug.cgi?id=215525 > 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 > @@ -577,6 +577,8 @@ 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) { > @@ -586,7 +588,7 @@ 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 > @@ -660,8 +662,7 @@ 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); > >
