Re: [RFC PATCH 04/19] vfio/pci: Serialize function reset with recovery

[sashiko-bot@kernel.org]

> Add a function reset helper and use it for VFIO_DEVICE_RESET. A later
> patch routes the guest triggered config space FLR through it as well.
> That path never did the power state transition, so make it optional.
> 
> With recovery enabled, take recovery_lock for writing, refuse the reset
> with -EBUSY if access is already blocked, otherwise block access and drop
> the lock again before revoking mappings or running the reset.
> recovery_lock cannot be held across the reset because a reset method can
> take pci_bus_sem, and the PCI error callbacks take recovery_lock from
> under it.
> 
> Dropping it is safe in both directions. The error callbacks hold
> recovery_lock for their whole body, so one already running has finished
> before the reset starts. One which arrives while the lock is down runs
> its own event, and the PCI core calls it with the device lock held, which
> [ ... ]
> fault path, which waits there rather than failing the fault while a
> reset is in flight.
> 
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Shameer Kolothum <skolothumtho@nvidia.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260901093217.8539-1-skolothumtho@nvidia.com?part=4