On 11/20/19 4:20 PM, Stuart Hayes wrote: > Without this patch, a pciehp hotplug port can stop generating interrupts > on hotplug events, so device adds and removals will not be seen. > > The pciehp interrupt handler pciehp_isr() will read the slot status > register and then write back to it to clear the bits that caused the > interrupt. If a different interrupt event bit gets set between the read and > the write, pciehp_isr will exit without having cleared all of the interrupt > event bits. If this happens, and the port is using an MSI interrupt where > per-vector masking is not supported, we won't get any more hotplug > interrupts from that device. > > That is expected behavior, according to the PCI Express Base Specification > Revision 5.0 Version 1.0, section 6.7.3.4, "Software Notification of Hot- > Plug Events". > > Because the "presence detect changed" and "data link layer state changed" > event bits are both getting set at nearly the same time when a device is > added or removed, this is more likely to happen than it might seem. The > issue was found (and can be reproduced rather easily) by connecting and > disconnecting an NVMe storage device on at least one system model. > > This issue was found while adding and removing various NVMe storage devices > on an AMD PCIe port (PCI device 0x1022/0x1483). > > This patch fixes this issue by modifying pciehp_isr() by looping back and > re-reading the slot status register immediately after writing to it, until > it sees that all of the event status bits have been cleared. > > Signed-off-by: Stuart Hayes <stuart.w.hayes@xxxxxxxxx> > --- > v2: > * fixed ctrl_warn() call > * improved comments > * added pvm_capable flag and changed pciehp_isr() to loop back only when > pvm_capable flag not set (suggested by Lukas Wunner) > > drivers/pci/hotplug/pciehp.h | 3 ++ > drivers/pci/hotplug/pciehp_hpc.c | 50 ++++++++++++++++++++++++++++---- > 2 files changed, 47 insertions(+), 6 deletions(-) > Bjorn, Please let me know if I could do anything to help get this patch accepted. Thanks! Stuart
