Message ID | 66eaeef31d4997ceea357ad93259f290ededecfd.1637187226.git.lukas@wunner.de |
---|---|
State | New |
Headers | show |
Series | PCI: pciehp: Fix infinite loop in IRQ handler upon power fault | expand |
On Wed, Nov 17, 2021 at 11:22:09PM +0100, Lukas Wunner wrote: > 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. > > Fixes: 8edf5332c393 ("PCI: pciehp: Fix MSI interrupt race") > Link: https://bugzilla.kernel.org/show_bug.cgi?id=214989 > Link: https://lore.kernel.org/linux-pci/DM8PR11MB5702255A6A92F735D90A4446868B9@DM8PR11MB5702.namprd11.prod.outlook.com > Reported-by: Joseph Bao <joseph.bao@intel.com> > Tested-by: Joseph Bao <joseph.bao@intel.com> > Signed-off-by: Lukas Wunner <lukas@wunner.de> > Cc: stable@vger.kernel.org # v4.19+ > Cc: Stuart Hayes <stuart.w.hayes@gmail.com> Applied to pci/hotplug for v5.17, thanks very much! > --- > drivers/pci/hotplug/pciehp_hpc.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c > index 83a0fa119cae..9535c61cbff3 100644 > --- a/drivers/pci/hotplug/pciehp_hpc.c > +++ b/drivers/pci/hotplug/pciehp_hpc.c > @@ -642,6 +642,8 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id) > */ > 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 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id) > } > > 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, void *dev_id) > } > > /* 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); > -- > 2.33.0 >
diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index 83a0fa119cae..9535c61cbff3 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -642,6 +642,8 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id) */ 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 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id) } 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, void *dev_id) } /* 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);