vfio/pci: Use RCU for error/request triggers to avoid circular locking

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Thanks to a device generating an ACS violation during bus reset,
lockdep reported the following circular locking issue:

CPU0: SET_IRQS (MSI/X): holds igate, acquires memory_lock
CPU1: HOT_RESET: holds memory_lock, acquires pci_bus_sem
CPU2: AER: holds pci_bus_sem, acquires igate

This results in a potential 3-way deadlock.

Remove the pci_bus_sem->igate leg of the triangle by using RCU
to peek at the eventfd rather than locking it with igate.

Fixes: 3be3a074cf ("vfio-pci: Don't use device_lock around AER interrupt setup")
Signed-off-by: Alex Williamson <alex.williamson@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20251124223623.2770706-1-alex@shazbot.org
Signed-off-by: Alex Williamson <alex@shazbot.org>

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Alex Williamson 2025-11-24 15:36:22 -07:00 • committed by Alex Williamson

parent fa804aa4ac

commit 98693e0897

4 changed files with 93 additions and 41 deletions

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68

drivers/vfio/pci/vfio_pci_core.c

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52

drivers/vfio/pci/vfio_pci_intrs.c

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4

drivers/vfio/pci/vfio_pci_priv.h

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10

include/linux/vfio_pci_core.h

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