[PATCH v2 0/7] s390: vfio-ccw fixes

Eric Farman
2019-05-14T23:43:04Z

The attached are a few fixes to the vfio-ccw kernel code for potential
errors or architecture anomalies. Under normal usage, and even most
abnormal usage, they don't expose any problems to a well-behaved guest
and its devices. But, they are deficiencies just the same and could
cause some weird behavior if they ever popped up in real life.

I have tried to arrange these patches in a "solves a noticeable problem
with existing workloads" to "solves a theoretical problem with
hypothetical workloads" order. This way, the bigger ones at the end
can be discussed without impeding the smaller and more impactful ones
at the start.

Per the conversations on patch 7, the last several patches remain
unchanged. They continue to buid an IDAL for each CCW, and only pin
guest pages and assign the resulting addresses to IDAWs if they are
expected to cause a data transfer. This will avoid sending an
unmodified guest address, which may be invalid but anyway is not mapped
to the same host address, in the IDAL sent to the channel subsystem and
any unexpected behavior that may result.

They are based on 5.1.0, not Conny's vfio-ccw tree even though there are
some good fixes pending for 5.2 there. I've run this series both with
and without that code, but couldn't decide which base would provide an
easier time applying patches. "I think" they should apply fine to both,
but I apologize in advance if I guessed wrong! :)

Changelog:
v1 -> v2:
- Patch 1:
- [Cornelia] Added a code comment about why we update the SCSW when
we've gone past the end of the chain for normal, successful, I/O
- Patch 2:
- [Cornelia] Cleaned up the cc info in the commit message
- [Pierre] Added r-b
- Patch 3:
- [Cornelia] Update the return code information in prologue of
pfn_array_pin(), and then only call vfio_unpin_pages() if we
pinned anything, rather than silently creating an error
(this last bit was mentioned on patch 6, but applied here)
- [Eric] Clean up the error exit in pfn_array_pin()
- Patch 4-7 unchanged

Eric Farman (7):
s390/cio: Update SCSW if it points to the end of the chain
s390/cio: Set vfio-ccw FSM state before ioeventfd
s390/cio: Split pfn_array_alloc_pin into pieces
s390/cio: Initialize the host addresses in pfn_array
s390/cio: Allow zero-length CCWs in vfio-ccw
s390/cio: Don't pin vfio pages for empty transfers
s390/cio: Remove vfio-ccw checks of command codes

drivers/s390/cio/vfio_ccw_cp.c | 159 +++++++++++++++++++++++---------
drivers/s390/cio/vfio_ccw_drv.c | 6 +-
2 files changed, 119 insertions(+), 46 deletions(-)

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2.17.1