linux-kernel - Re: [PATCH v2 5/5] vfio: ccw: add traceponits for interesting error paths

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Date:   Mon, 30 Apr 2018 18:51:54 +0200
From:   Halil Pasic <pasic@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     Dong Jia Shi <bjsdjshi@...ux.vnet.ibm.com>,
        Halil Pasic <pasic@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, borntraeger@...ibm.com,
        bjsdjshi@...ux.ibm.com, pmorel@...ux.ibm.com
Subject: Re: [PATCH v2 5/5] vfio: ccw: add traceponits for interesting error
 paths



On 04/30/2018 05:03 PM, Cornelia Huck wrote:
>> I think the naming of this fctl thing is a bit cryptic,
>> but if we don't see this as ABI I'm fine with it -- can be improved.
>> What would be a better name? I was thinking along the lines accept_request.
>> (Bad error code would mean that the request did not get accepted. Good
>> code does not mean the requested function was performed successfully.)
> I think fctl is fine (if you don't understand what 'fctl' is, you're
> unlikely to understand it even if it were named differently.)
> 

AFAIU this fctl is a bit more complicated than the normal fctl. But
better let sleeping dogs lie.

>> Also I think vfio_ccw_io_fctl with no zero error code would make sense
>> as dev_warn. If I were an admin looking into a problem I would very much
>> appreciate seeing something in the messages log (and not having to enable
>> tracing first). This point seems to be a good one for high level 'request gone
>> bad' kind of report. Opinions?
> I'd also exclude -EOPNOTSUPP (as this also might happen with e.g. a halt/clear enabled user space, which probes availability of halt/clear support by giving it a try once (yes, I really want to post my patches this week.))
> 

I'm looking forward to the clear/halt. It hope it will help me understand
the big vfio-ccw picture better. There are still dark spots, but I don't
feel like doing something against this, as there is quite some activity
going on here -- and I don't want to hamper the efforts by binding resources.

Regards,
Halil