Re: [RFC PATCH v3 01/20] vfio/pci: Add SRCU-protected access ops

[sashiko-bot@kernel.org]

> Before recovering a device, VFIO needs to stop new hardware accesses and
> wait for operations already in progress to finish.
> 
> Give each open device an SRCU instance to track hardware accesses.
> Enable SRCU access tracking only for devices with
> pci_recovery_supported set.
> Select and call the access operation within the same SRCU read-side
> section. Keep copies to and from userspace outside that section so a
> page fault cannot hold up recovery.
> 
> Introduce live and blocked tables. Initialize the ops pointer to blocked
> when the device is created, and select live ops when open finishes.
> Close uses a blocking transition that installs blocked ops and drains
> SRCU readers before teardown. Open publishes live ops after setup.
> Serialize these transitions with access_lock. Internal setup and cleanup
> use their own helpers.
> 
> Provide an accessor for operations that use their existing synchronization
> instead of SRCU. The accessor only returns the selected table. It does
> not acquire a lock or keep the device's per-open resources alive.
> 
> Subsequent patches convert hardware access paths to these ops and add
> support for host PCI error recovery using the same blocked table.
> 
> Signed-off-by: Shameer Kolothum <skolothumtho@nvidia.com>

Sashiko has reviewed this patch and found no issues.

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