ACK: [SRU][F][PATCH 1/1] s390/pci: ignore stale configuration request event

[Kleber Souza]

On 03.09.20 11:57, frank.heimes at canonical.com wrote:
> From: Niklas Schnelle <schnelle at linux.ibm.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1893778
> 
> A configuration request event may be stale, that is the event
> may reference a zdev which was already configured.
> This can happen when a hotplug happens during boot such that
> the device is discovered and configured in the initial clp_list_pci(),
> then after initialization we enable events and process
> the original configuration request which additionally still contains
> the old disabled function handle leading to a failure during device
> enablement and subsequent I/O lockout.
> 
> Fix this by restoring the check that the device to be configured is in
> standby which was removed in commit f606b3ef47c9 ("s390/pci: adapt events
> for zbus").
> 
> This check does not need serialization as we only enable the events after
> zPCI has fully initialized, which includes the initial clp_list_pci(),
> rescan only does updates and events are serialized with respect to each
> other.
> 
> Fixes: f606b3ef47c9 ("s390/pci: adapt events for zbus")
> Cc: <stable at vger.kernel.org> # 5.8
> Reported-by: Shalini Chellathurai Saroja <shalini at linux.ibm.com>
> Tested-by: Shalini Chellathurai Saroja <shalini at linux.ibm.com>
> Acked-by: Pierre Morel <pmorel at linux.ibm.com>
> Signed-off-by: Niklas Schnelle <schnelle at linux.ibm.com>
> Signed-off-by: Heiko Carstens <hca at linux.ibm.com>
> (cherry picked from commit b76fee1bc56c31a9d2a49592810eba30cc06d61a)
> Signed-off-by: Frank Heimes <frank.heimes at canonical.com>

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

> ---
>  arch/s390/pci/pci_event.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/s390/pci/pci_event.c b/arch/s390/pci/pci_event.c
> index 538da3faa048..9a3a291cad43 100644
> --- a/arch/s390/pci/pci_event.c
> +++ b/arch/s390/pci/pci_event.c
> @@ -92,6 +92,9 @@ static void __zpci_event_availability(struct zpci_ccdf_avail *ccdf)
>  			ret = clp_add_pci_device(ccdf->fid, ccdf->fh, 1);
>  			break;
>  		}
> +		/* the configuration request may be stale */
> +		if (zdev->state != ZPCI_FN_STATE_STANDBY)
> +			break;
>  		zdev->fh = ccdf->fh;
>  		zdev->state = ZPCI_FN_STATE_CONFIGURED;
>  		ret = zpci_enable_device(zdev);
>