Re: [PATCH 0/4] vfio: ccw: error handling fixes and improvements

Cornelia Huck
2018-03-26T09:02:24Z

On Wed, 21 Mar 2018 03:08:18 +0100
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:

> Hi Conny,
>
> Halil reported a host crash when using vfio-ccw. The root cause of the problem
> is that vfio_pin_pages fails with EINVAL for reasons unknown. He has
> experienced such failures after online-ing a dasd in the guest (the dasd has 3
> partitions, hat may or may not have any significance). The problem isn't
> experienced on every attempt to online the dasd, and breaking at css_do_ssch
> seems to make things work.
>
> One thing is sure: the host kernel should not crash under the described
> circumstances.
>
> To fix the problem, the first patch of this series fixes the cleanup when
> cp_prefetch fails in the higher level. The 2nd and the 3rd patches provide
> correctness and denfensive actions for the interfaces in the lower level.

So, is the first patch stable material?

>
> The 4th patch is trying to add tracepoints for vfio-ccw, so that we can debug
> such issue easier in future.

Tracepoints are nice :)

>
> For details see the commit message portions of the inividual patches.

Still digging through the post-vacation mail pile, will do more looking
later.

> Thanks.
>
> Dong Jia Shi (2):
> vfio: ccw: refactor and improve pfn_array_alloc_pin()
> vfio: ccw: set ccw->cda to NULL defensively
>
> Halil Pasic (2):
> vfio: ccw: fix cleanup if cp_prefetch fails
> vfio: ccw: add traceponits for interesting error paths
>
> drivers/s390/cio/Makefile | 1 +
> drivers/s390/cio/vfio_ccw_cp.c | 121 ++++++++++++++++++++------------------
> drivers/s390/cio/vfio_ccw_fsm.c | 13 ++++
> drivers/s390/cio/vfio_ccw_trace.h | 86 +++++++++++++++++++++++++++
> 4 files changed, 163 insertions(+), 58 deletions(-)
> create mode 100644 drivers/s390/cio/vfio_ccw_trace.h
>