On Mon, 2020-01-20 at 10:10 -0600, Stuart Hayes wrote: > 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 > Hi, can someone please review/accept this patch please? It fixes NVMe hotplug operations in SLES15-SP1. Thanks, Enzo
