Re: [PATCH 1/5] PCI: Add disconnected device checks to user config reads

[sashiko-bot@kernel.org]

> Since commit 4b1038834739 ("PCI: Don't attempt config access to
> disconnected devices") the kernel config read accessors skip devices
> marked disconnected, returning PCIBIOS_DEVICE_NOT_FOUND and ~0 data.
> The user config read accessors still issue the read, and if the host
> bridge completes it with ~0 data and no error, they report success.
> 
> Check pci_dev_is_disconnected() in pci_user_read_config_*() as well,
> failing with -ENODEV and ~0 data. Do the check after waiting for any
> pci_cfg_access_lock() holder so a reader blocked behind a reset also
> sees a device that was disconnected while it waited.
> 
> This prepares for converting sysfs attributes from the kernel
> accessors to the user accessors so they keep skipping disconnected
> devices.
> 
> On a disconnected device, existing callers of the user read accessors
> now behave as follows:
> 
>   - The sysfs "config" file and /proc/bus/pci ignore the return value
>     and return the same ~0 data as before
>   - pciconfig_read() fails with -EIO
>   - VPD reads and VFIO config reads fail with -ENODEV instead of
>     returning ~0 data
>   - VPD writes fail with -ENODEV instead of timing out with a
>     "firmware bug" warning
>   - VFIO writes to PCI_COMMAND fail with -ENODEV, since VFIO reads the
>     current value first
> 
> Signed-off-by: Matthew Wood <thepacketgeek@gmail.com>

Sashiko has reviewed this patch and found no issues.

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