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Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH |
Date: |
Wed, 6 Sep 2017 13:25:38 +0200 |
On Wed, 6 Sep 2017 16:27:20 +0800
Dong Jia Shi <address@hidden> wrote:
> * Halil Pasic <address@hidden> [2017-09-05 19:20:43 +0200]:
>
> >
> >
> > On 09/05/2017 05:46 PM, Cornelia Huck wrote:
> > > On Tue, 5 Sep 2017 17:24:19 +0200
> > > Halil Pasic <address@hidden> wrote:
> > >
> > >> My problem with a program check (indicated by SCSW word 2 bit 10) is
> > >> that, in my reading of the architecture, the semantic behind it is: The
> > >> channel subsystem (not the cu or device) has detected, that the
> > >> the channel program (previously submitted as an ORB) is erroneous. Which
> > >> programs are erroneous is specified by the architecture. What we have
> > >> here does not qualify.
> > >>
> > >> My idea was to rather blame the virtual hardware (device) and put no
> > >> blame
> > >> on the program nor he channel subsystem. This could be done using device
> > >> status (unit check with command reject, maybe unit exception) or
> > >> interface
> > >> check. My train of thought was, the problem is not consistent across a
> > >> device type, so it has to be device specific.
> > >
> > > Unit exception might be a better way to express what is happening here.
> > > At least, it moves us away from cc 1 and not towards cc 3 :)
> > >
> >
> > I will do a follow up patch pursuing device exception.
> >
> > >>
> > >> Of course blaming the device could mislead the person encountering the
> > >> problem, and make him believe it's an non-virtual hardware problem.
> > >>
> > >> About the misleading, I think the best we can do is log out a message
> > >> indicating what really happened.
> > >
> > > Just document it in the code? If it doesn't happen with Linux as a
> > > guest, it is highly unlikely to be seen in the wild.
> > >
> >
> >
> > Well we have two problems here:
> > 1) Unit exception can be already defined by the device type for the
> > command (reference:
> > http://publibfp.dhe.ibm.com/cgi-bin/bookmgr/BOOKS/dz9ar110/2.6.10?DT=19920904110920).
> > I think this one is what you mean. And I agree that's best handled
> > with comment in code.
> Using unit check, with bit 3 byte 0 of the sense data set to 1, to
> indicate an 'Equipment check', sounds a bit more proper than unit
> exception.
I don't agree: Equipment check sounds a lot more dire (and seems to
imply a malfunction). I like unit exception better.
>
> > 2) The poor user/programmer is trying to figure out why things
> > don't work (why are we getting the unit exception)? I think that's
> > best remedied with producing something for the log (maybe a warning
> > with warn_report which states that the implementation vfio-ccw requires
> > the given flags).
> Fine with me.
With me as well.
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Cornelia Huck, 2017/09/05
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Halil Pasic, 2017/09/05
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Cornelia Huck, 2017/09/05
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Halil Pasic, 2017/09/05
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Dong Jia Shi, 2017/09/06
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH,
Cornelia Huck <=
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Dong Jia Shi, 2017/09/07
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Halil Pasic, 2017/09/07
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Cornelia Huck, 2017/09/13
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Halil Pasic, 2017/09/13
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Cornelia Huck, 2017/09/06
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Dong Jia Shi, 2017/09/06
- Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH, Cornelia Huck, 2017/09/06