Re: [PATCH 0/1] vfio-ccw: Fix garbage sense data on I/O error

[Cornelia Huck <cohuck@redhat.com>]

On Thu, Jun 10 2021, Eric Farman <farman@linux.ibm.com> wrote:

> Hi Conny,
>
> Per our offline discussion, here's a fix for the error when a guest
> issues "dasdfmt -M quick". It basically reverts commit 334e76850bbb
> ("vfio/ccw: update sense data if a unit check is pending")
> and modifies the check that builds sense data in the TSCH handler.
>
> I opted to NOT disable PMCW.CSENSE, because doing so prevents
> vfio-ccw devices from coming online at all (didn't pursue deep
> enough to explain why). Turning it off in reaction to a unit
> check (in this now-reverted codepath) works, but only because of
> the corresponding PMCW.CSENSE check in the TSCH code.

It's a bit puzzling why fencing it off in msch doesn't work; but maybe
it would not be the right thing to do anyway, if we can support some
concurrent sense operations. I'm still reading the PoP.

>
> I don't know if anything is needed for the (unaltered) ECW data
> that commit b498484ed49a ("s390x/css: sense data endianness")
> addressed for the copied sense_data bytes, but figure we can
> use this as a starting point. Thoughts?
>
> Eric Farman (1):
>   vfio-ccw: Keep passthrough sense data intact
>
>  hw/s390x/css.c | 3 ++-
>  hw/vfio/ccw.c  | 6 ------
>  2 files changed, 2 insertions(+), 7 deletions(-)
>