[RFC PATCH v7 0/4] fix vt-d hard lockup when hotplug ATS capable device

[Ethan Zhao <haifeng.zhao@linux.intel.com>]

This patchset is used to fix vt-d hard lockup reported when surprise
unplug ATS capable endpoint device connects to system via PCIe switch
as following topology.

     +-[0000:15]-+-00.0  Intel Corporation Ice Lake Memory Map/VT-d
     |           +-00.1  Intel Corporation Ice Lake Mesh 2 PCIe
     |           +-00.2  Intel Corporation Ice Lake RAS
     |           +-00.4  Intel Corporation Device 0b23
     |           \-01.0-[16-1b]----00.0-[17-1b]--+-00.0-[18]----00.0
                                           NVIDIA Corporation Device 2324
     |                                           +-01.0-[19]----00.0
                          Mellanox Technologies MT2910 Family [ConnectX-7]

User brought endpoint device 19:00.0's link down by flapping it's hotplug
capable slot 17:01.0 link control register, as sequence DLLSC response,
pciehp_ist() will unload device driver and power it off, durning device 
driver is unloading an iommu device-TLB invalidation (Intel vt-d spec, or
'ATS invalidation' in PCIe spec) request issued to that link down device,
thus a long time completion/timeout waiting in interrupt context causes
continuous hard lockup warnning and system hang.

Other detail, see every patch commit log.

patch [3&4] were tested by yehaorong@bytedance.com on stable v6.7-rc4.
patch [1&2] only passed compiling on stable v6.7-rc6.


change log:
v7:
- reorder patches and revise commit log per Bjorn's guide.
- other code and commit log revise per Lukas' suggestion.
- rebased to stable v6.7-rc6.
v6:
- add two patches to break out device-TLB invalidation if device is gone.
v5:
- add a patch try to fix the rare case (surprise remove a device in
  safe removal process). not work because surprise removal handling can't
  re-enter when another safe removal is in process.
v4:
- move the PCI device state checking after ATS per Baolu's suggestion.
v3:
- fix commit description typo.
v2:
- revise commit[1] description part according to Lukas' suggestion.
- revise commit[2] description to clarify the issue's impact.
v1:
- https://lore.kernel.org/lkml/20231213034637.2603013-1-haifeng.zhao@
linux.intel.com/T/


Thanks,
Ethan


Ethan Zhao (4):
  iommu/vt-d: add flush_target_dev member to struct intel_iommu and pass
    device info to all ATS invalidation functions
  iommu/vt-d: break out device-TLB invalidation if target device is gone
  PCI: make pci_dev_is_disconnected() helper public for other drivers
  iommu/vt-d: don't issue device-TLB invalidate request when device is
    disconnected

 drivers/iommu/intel/dmar.c  | 12 ++++++++++++
 drivers/iommu/intel/iommu.c |  1 +
 drivers/iommu/intel/iommu.h |  2 ++
 drivers/iommu/intel/pasid.c |  4 ++++
 drivers/iommu/intel/svm.c   |  1 +
 drivers/pci/pci.h           |  5 -----
 include/linux/pci.h         |  5 +++++
 7 files changed, 25 insertions(+), 5 deletions(-)

-- 
2.31.1