25216afc9d ("PCI: Add managed pcim_intx()") moved the allocation step for
pci_intx()'s device resource from pcim_enable_device() to pcim_intx(). As
before, pcim_enable_device() sets pci_dev.is_managed to true; and it is
never set to false again.
Due to the lifecycle of a struct pci_dev, it can happen that a second
driver obtains the same pci_dev after a first driver ran. If one driver
uses pcim_enable_device() and the other doesn't, this causes the other
driver to run into managed pcim_intx(), which will try to allocate when
called for the first time.
Allocations might sleep, so calling pci_intx() while holding spinlocks
becomes then invalid, which causes lockdep warnings and could cause
deadlocks:
========================================================
WARNING: possible irq lock inversion dependency detected
6.11.0-rc6+ #59 Tainted: G W
--------------------------------------------------------
CPU 0/KVM/1537 just changed the state of lock:
ffffa0f0cff965f0 (&vdev->irqlock){-...}-{2:2}, at:
vfio_intx_handler+0x21/0xd0 [vfio_pci_core] but this lock took another,
HARDIRQ-unsafe lock in the past: (fs_reclaim){+.+.}-{0:0}
and interrupts could create inverse lock ordering between them.
other info that might help us debug this:
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(fs_reclaim);
local_irq_disable();
lock(&vdev->irqlock);
lock(fs_reclaim);
<Interrupt>
lock(&vdev->irqlock);
*** DEADLOCK ***
Have pcim_enable_device()'s release function, pcim_disable_device(), set
pci_dev.is_managed to false so that subsequent drivers using the same
struct pci_dev do not implicitly run into managed code.
Link: https://lore.kernel.org/r/20240905072556.11375-2-pstanner@redhat.com
Fixes: 25216afc9d ("PCI: Add managed pcim_intx()")
Reported-by: Alex Williamson <alex.williamson@redhat.com>
Closes: https://lore.kernel.org/all/20240903094431.63551744.alex.williamson@redhat.com/
Suggested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Philipp Stanner <pstanner@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
fc8c818e75