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Subject[PATCH v6 0/5] Fix DPC hotplug race and enhance error handling

This simple patch set fixed some serious security issues found when DPC
error injection and NVMe SSD hotplug brute force test were doing -- race
condition between DPC handler and pciehp, AER interrupt handlers, caused
system hang and system with DPC feature couldn't recover to normal
working state as expected (NVMe instance lost, mount operation hang,
race PCIe access caused uncorrectable errors reported alternatively etc).

With this patch set applied, stable 5.9-rc6 on ICS (Ice Lake SP platform,

could pass the PCIe Gen4 NVMe SSD brute force hotplug test with any time
interval between hot-remove and plug-in operation tens of times without
any errors occur and system works normal.

With this patch set applied, system with DPC feature could recover from
NON-FATAL and FATAL errors injection test and works as expected.

System works smoothly when errors happen while hotplug is doing, no
uncorrectable errors found.

Brute DPC error injection script:

for i in {0..100}
setpci -s 64:02.0 0x196.w=000a
setpci -s 65:00.0 0x04.w=0544
mount /dev/nvme0n1p1 /root/nvme
sleep 1

Other details see every commits description part.

This patch set could be applied to stable 5.9-rc6/rc7 directly.

Help to review and test.

v2: changed according to review by Andy Shevchenko.
v3: changed patch 4/5 to simpler coding.
v4: move function pci_wait_port_outdpc() to DPC driver and its
declaration to pci.h. (tip from Christoph Hellwig <>).
v5: fix building issue reported by with some config.
v6: move patch[3/5] as the first patch according to Lukas's suggestion.
and rewrite the comment part of patch[3/5].

Ethan Zhao (5):
PCI/ERR: get device before call device driver to avoid NULL pointer
PCI/DPC: define a function to check and wait till port finish DPC
PCI: pciehp: check and wait port status out of DPC before handling
PCI: only return true when dev io state is really changed
PCI/ERR: don't mix io state not changed and no driver together

drivers/pci/hotplug/pciehp_hpc.c | 4 +++-
drivers/pci/pci.h | 39 ++++++--------------------------
drivers/pci/pcie/dpc.c | 27 ++++++++++++++++++++++
drivers/pci/pcie/err.c | 18 +++++++++++++--
4 files changed, 53 insertions(+), 35 deletions(-)

base-commit: a1b8638ba1320e6684aa98233c15255eb803fac7

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