diff options
| author | Alex Williamson <alex.williamson@nvidia.com> | 2025-11-24 15:36:22 -0700 |
|---|---|---|
| committer | Alex Williamson <alex@shazbot.org> | 2025-11-28 10:04:27 -0700 |
| commit | 98693e0897f754e3f51ce6626ed5f785f625ba2b (patch) | |
| tree | 634b57ae01e46282b1b2f869bdf1e418b5caaf79 /include | |
| parent | fa804aa4ac1b091ef2ec2981f08a1c28aaeba8e7 (diff) | |
vfio/pci: Use RCU for error/request triggers to avoid circular locking
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: 3be3a074cf5b ("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>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/vfio_pci_core.h | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h index 88fd2fd895d0..a1eddd55dab8 100644 --- a/include/linux/vfio_pci_core.h +++ b/include/linux/vfio_pci_core.h @@ -12,6 +12,7 @@ #include <linux/pci.h> #include <linux/vfio.h> #include <linux/irqbypass.h> +#include <linux/rcupdate.h> #include <linux/types.h> #include <linux/uuid.h> #include <linux/notifier.h> @@ -29,6 +30,11 @@ struct vfio_pci_region; struct p2pdma_provider; struct dma_buf_phys_vec; +struct vfio_pci_eventfd { + struct eventfd_ctx *ctx; + struct rcu_head rcu; +}; + struct vfio_pci_regops { ssize_t (*rw)(struct vfio_pci_core_device *vdev, char __user *buf, size_t count, loff_t *ppos, bool iswrite); @@ -124,8 +130,8 @@ struct vfio_pci_core_device { struct pci_saved_state *pci_saved_state; struct pci_saved_state *pm_save; int ioeventfds_nr; - struct eventfd_ctx *err_trigger; - struct eventfd_ctx *req_trigger; + struct vfio_pci_eventfd __rcu *err_trigger; + struct vfio_pci_eventfd __rcu *req_trigger; struct eventfd_ctx *pm_wake_eventfd_ctx; struct list_head dummy_resources_list; struct mutex ioeventfds_lock; |