ACK: [SRU][F][PATCH 1/1] s390/pci: fix leak of DMA tables on hard unplug

[Stefan Bader]

On 21.09.20 16:43, frank.heimes at canonical.com wrote:
> From: Niklas Schnelle <schnelle at linux.ibm.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1896216
> 
> commit f606b3ef47c9 ("s390/pci: adapt events for zbus") removed the
> zpci_disable_device() call for a zPCI event with PEC 0x0304 because
> the device is already deconfigured by the platform.
> This however skips the Linux side of the disable in particular it leads
> to leaking the DMA tables and bitmaps because zpci_dma_exit_device() is
> never called on the device.
> 
> If the device transitions to the Reserved state we call zpci_zdev_put()
> but zpci_release_device() will not call zpci_disable_device() because
> the state of the zPCI function is already ZPCI_FN_STATE_STANDBY.
> 
> If the device is put into the Standby state, zpci_disable_device() is
> not called and the device is assumed to have been put in Standby through
> platform action.
> At this point the device may be removed by a subsequent event with PEC
> 0x0308 or 0x0306 which calls zpci_zdev_put() with the same problem
> as above or the device may be configured again in which case
> zpci_disable_device() is also not called.
> 
> Fix this by calling zpci_disable_device() explicitly for PEC 0x0304 as
> before. To make it more clear that zpci_disable_device() may be called,
> even if the lower level device has already been disabled by the
> platform, add a comment to zpci_disable_device().
> 
> Cc: <stable at vger.kernel.org> # 5.8
> Fixes: f606b3ef47c9 ("s390/pci: adapt events for zbus")
> Signed-off-by: Niklas Schnelle <schnelle at linux.ibm.com>
> Signed-off-by: Vasily Gorbik <gor at linux.ibm.com>
> (cherry picked from commit afdf9550e54627fcf4dd609bdc1153059378cdf5 linux-next)
> Signed-off-by: Frank Heimes <frank.heimes at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---
>  arch/s390/pci/pci.c       | 4 ++++
>  arch/s390/pci/pci_event.c | 2 ++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
> index fb25665ec44b..f3a477f919d0 100644
> --- a/arch/s390/pci/pci.c
> +++ b/arch/s390/pci/pci.c
> @@ -709,6 +709,10 @@ EXPORT_SYMBOL_GPL(zpci_enable_device);
>  int zpci_disable_device(struct zpci_dev *zdev)
>  {
>  	zpci_dma_exit_device(zdev);
> +	/*
> +	 * The zPCI function may already be disabled by the platform, this is
> +	 * detected in clp_disable_fh() which becomes a no-op.
> +	 */
>  	return clp_disable_fh(zdev);
>  }
>  EXPORT_SYMBOL_GPL(zpci_disable_device);
> diff --git a/arch/s390/pci/pci_event.c b/arch/s390/pci/pci_event.c
> index 9a3a291cad43..d9ae7456dd4c 100644
> --- a/arch/s390/pci/pci_event.c
> +++ b/arch/s390/pci/pci_event.c
> @@ -143,6 +143,8 @@ static void __zpci_event_availability(struct zpci_ccdf_avail *ccdf)
>  			zpci_remove_device(zdev);
>  		}
>  
> +		zdev->fh = ccdf->fh;
> +		zpci_disable_device(zdev);
>  		zdev->state = ZPCI_FN_STATE_STANDBY;
>  		if (!clp_get_state(ccdf->fid, &state) &&
>  		    state == ZPCI_FN_STATE_RESERVED) {
> 


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