Re: [PATCH 3/4] powerpc/eeh: Remove workaround from eeh_add_device_late()

[Oliver O'Halloran <oohall@gmail.com>]

On Mon, 2020-03-30 at 15:56 +1100, Sam Bobroff wrote:
> When EEH device state was released asynchronously by the device
> release handler, it was possible for an outstanding reference to
> prevent it's release and it was necessary to work around that if a
> device was re-discovered at the same PCI location.

I think this is a bit misleading. The main situation where you'll hit
this hack is when recovering a device with a driver that doesn't
implement the error handling callbacks. In that case the device is
removed, reset, then re-probed by the PCI core, but we assume it's the
same physical device so the eeh_device state remains active.

If you actually changed the underlying device I suspect something bad
would happen.

> Now that the state is released synchronously that is no longer
> possible and the workaround is no longer necessary.

You could probably fold this into the previous patch, but eh. You could
probably fold this into the previous patch, but eh.

> Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
> ---
>  arch/powerpc/kernel/eeh.c | 23 +----------------------
>  1 file changed, 1 insertion(+), 22 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
> index c36c5a7db5ca..12c248a16527 100644
> --- a/arch/powerpc/kernel/eeh.c
> +++ b/arch/powerpc/kernel/eeh.c
> @@ -1206,28 +1206,7 @@ void eeh_add_device_late(struct pci_dev *dev)
>  		eeh_edev_dbg(edev, "Device already referenced!\n");
>  		return;
>  	}
> -
> -	/*
> -	 * The EEH cache might not be removed correctly because of
> -	 * unbalanced kref to the device during unplug time, which
> -	 * relies on pcibios_release_device(). So we have to remove
> -	 * that here explicitly.
> -	 */
> -	if (edev->pdev) {
> -		eeh_rmv_from_parent_pe(edev);
> -		eeh_addr_cache_rmv_dev(edev->pdev);
> -		eeh_sysfs_remove_device(edev->pdev);
> -
> -		/*
> -		 * We definitely should have the PCI device removed
> -		 * though it wasn't correctly. So we needn't call
> -		 * into error handler afterwards.
> -		 */
> -		edev->mode |= EEH_DEV_NO_HANDLER;
> -
> -		edev->pdev = NULL;
> -		dev->dev.archdata.edev = NULL;
> -	}
> +	WARN_ON_ONCE(edev->pdev);
>  
>  	if (eeh_has_flag(EEH_PROBE_MODE_DEV))
>  		eeh_ops->probe(pdn, NULL);