On 9/5/24 16:25, Philipp Stanner wrote:
> commit 25216afc9db5 ("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 implicitly run into managed code.
>
> Fixes: 25216afc9db5 ("PCI: Add managed pcim_intx()")
> Reported-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Closes: https://lore.kernel.org/all/20240903094431.63551744.alex.williamson@xxxxxxxxxx/
> Suggested-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Signed-off-by: Philipp Stanner <pstanner@xxxxxxxxxx>
> Tested-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Looks OK to me.
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
--
Damien Le Moal
Western Digital Research
