ACK: [SRU][B][PATCH 0/2] zpcictl --reset - contribution for kernel (LP: 1870320)

[Kleber Souza]

On 13.05.20 18:22, frank.heimes at canonical.com wrote:
> Buglink: https://bugs.launchpad.net/bugs/1870320
> 
> SRU Justification:
> 
> [Impact]
> 
> * With zpci_disable() working, 'lockdep' detected a potential deadlock (in the s390x zPCI subsystem).
> 
> * The deadlock is between recovering a PCI function via the /sys/bus/pci/devices/<dev>/recover attribute vs powering it off via /sys/bus/pci/slots/<slot>/power.
> 
> [Fix]
> 
> * Backport 1: https://launchpadlibrarian.net/479554961/0001-s390-pci-Recover-handle-in-clp_set_pci_fn.patch
> 
> * Backport 2: https://launchpadlibrarian.net/478714295/0001-s390-pci-Fix-possible-deadlock-in-recover_store.patch
> 
> [Test Case]
> 
> * It's best to (re-)test using the kernel's locking validator, also known as 'lockdep'.
> 
> * Since this potential deadlock was identified by lockdep.
> 
> [Regression Potential] 
> 
> * The regression potential can be considered as moderate, since:
> 
> * It is purely s390x specific code (arch/s390/include/asm/pci.h and arch/s390/pci/{pci.c,pci_clp.c,pci_sysfs.c}).
> 
> * It only affects the zPCI, the s390x specific PCI code layer.
> 
> * PCI cards available for s390x are optional cards (RoCE and zEDC) and not very wide-spread.
> 
> * The states between such a deadlock can happen (recover and power off) are non standard and usually undesired states.
> 
> * The patches are upstream accepted since 5.6 and already landed in eoan and focal.
> 
> [Other Info]
> 
> * Patches 17cdec960cf7 "s390/pci: Recover handle in clp_set_pci_fn()" and 576c75e36c68 "s390/pci: Fix possible deadlock in recover_store()" are upstream accepted since kernel 5.6, but they don't apply cleanly on bionic master-next, hence backports are needed:
> 
> * 0001-s390-pci-Recover-handle-in-clp_set_pci_fn.patch is a backport of 17cdec960cf776b20b1fb08c622221babe591d51 17cdec960cf7 "s390/pci: Recover handle in clp_set_pci_fn()"
> 
> * 0001-s390-pci-Fix-possible-deadlock-in-recover_store.patch is a backport of 576c75e36c689bec6a940e807bae27291ab0c0de 576c75e36c68 "s390/pci: Fix possible deadlock in recover_store()"
> 
> * Both patches/commits already landed in focal (with LP 1863768) and in eoan (with LP 1868324).
> 
> Niklas Schnelle (2):
>   s390/pci: Recover handle in clp_set_pci_fn()
>   s390/pci: Fix possible deadlock in recover_store()
> 
>  arch/s390/include/asm/pci.h |  2 +-
>  arch/s390/pci/pci.c         |  2 +-
>  arch/s390/pci/pci_clp.c     | 46 ++++++++++++++-------------
>  arch/s390/pci/pci_sysfs.c   | 63 ++++++++++++++++++++++++-------------
>  4 files changed, 69 insertions(+), 44 deletions(-)
> 

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