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

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Message-Id: <f9ab140d-871a-f284-f10a-62e608db10df@linux.vnet.ibm.com>
Date:   Mon, 26 Mar 2018 13:25:34 +0200
From:   Halil Pasic <pasic@...ux.vnet.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>,
        Dong Jia Shi <bjsdjshi@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, borntraeger@...ibm.com,
        pmorel@...ux.vnet.ibm.com
Subject: Re: [PATCH 0/4] vfio: ccw: error handling fixes and improvements



On 03/26/2018 11:02 AM, Cornelia Huck wrote:
> On Wed, 21 Mar 2018 03:08:18 +0100
> Dong Jia Shi <bjsdjshi@...ux.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?

I think it should be.

> 
>>
>> 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
>>
>