[PATCH v2 0/6] pci-hyper: Fix race condition bugs for fast device hotplug

[Dexuan Cui <decui@microsoft.com>]

Before the guest finishes probing a device, the host may be already starting
to remove the device. Currently there are multiple race condition bugs in the
pci-hyperv driver, which can cause the guest to panic.  The patchset fixes
the crashes.

The patchset also does some cleanup work: patch 3 removes the useless
hv_pcichild_state, and patch 4 reverts an old patch which is not really
useful (without patch 4, it would be hard to make patch 5 clean).

Patch 6 removes the use of a global mutex lock, and enables async-probing
to allow concurrent device probing for faster boot.

In v2, I dropped the "debug code" before the real patch body to avoid
confusion; I fixed some minor issues pointed out by Michael Kelely:
fixed "goto release_state_lock" in patch 5, and improved the commit log
of patch 6; I added Wei Hu's Acked-by to patch 4. I added the cc:stable
tag to all the 6 patches.

v2 is based on v6.3-rc5.

I have been testing the patchset with
https://lwn.net/ml/linux-kernel/20230316091540.494366-1-alexander.stein%40ew.tq-group.com/
for several days, and no panic/hang is observed (earlier the kernel
would panic/hang within 1 day in my long haul testing).

The patchset is also availsble in my github branch:
https://github.com/dcui/tdx/commits/decui/vpci/v6.3-rc5-v2

v1 can be found here:
https://lwn.net/ml/linux-kernel/20230328045122.25850-1-decui%40microsoft.com/

Please review. Thanks!

Dexuan Cui (6):
  PCI: hv: Fix a race condition bug in hv_pci_query_relations()
  PCI: hv: Fix a race condition in hv_irq_unmask() that can cause panic
  PCI: hv: Remove the useless hv_pcichild_state from struct hv_pci_dev
  Revert "PCI: hv: Fix a timing issue which causes kdump to fail
    occasionally"
  PCI: hv: Add a per-bus mutex state_lock
  PCI: hv: Use async probing to reduce boot time

 drivers/pci/controller/pci-hyperv.c | 145 +++++++++++++++++-----------
 1 file changed, 86 insertions(+), 59 deletions(-)

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2.25.1