Re: [PATCH 5/7] scsi: Add mapping for generic SCSI_HOST status to sense codes

[Hannes Reinecke]

On 11/16/20 9:05 PM, Paolo Bonzini wrote:
> On 16/11/20 20:03, Hannes Reinecke wrote:
> > > > +        case SCSI_HOST_TARGET_FAILURE:
> > > > +            *sense = SENSE_CODE(TARGET_FAILURE);
> > > > +            return CHECK_CONDITION;
> > > > +        case SCSI_HOST_RESERVATION_ERROR:
> > > > +            return RESERVATION_CONFLICT;
> > > > +        case SCSI_HOST_ALLOCATION_FAILURE:
> > > > +            *sense = SENSE_CODE(SPACE_ALLOC_FAILED);
> > > > +            return CHECK_CONDITION;
> > > > +        case SCSI_HOST_MEDIUM_ERROR:
> > > > +            *sense = SENSE_CODE(READ_ERROR);
> > > > +            return CHECK_CONDITION;
> > >
> > > Can these actually be visible to userspace?  I'd rather avoid having 
> > > them in QEMU if possible.
> > >
> > > Otherwise, the patches are completely sensible.
> > And I did it exactly for the opposite purpose: rather than 
> > painstakingly figuring out which codes _might_ be returned (and be 
> > utterly surprised if we missed some) add an interpretation for every 
> > _possible_ code, avoiding nasty surprises.
>
> And that certainly makes sense too.
>
> On the other hand it'd be nice if Linux was clearer about which the 
> SCSI_HOST values are part of the userspace API and which are just an 
> (ugly) implementation detail.
Oh, I certainly agree with that.
But that is more of a long-term prospect; I do see some discussions 
ahead if one were to try it. Especially as (like DID_BAD_TARGET and
DID_NO_CONNECT) have no clear distinction between them, and are used 
more-or-less interchangeably.

But a clear definition of these values would inevitably lead to a change 
in various drivers, which then would lead to a change in behaviour, and 
a possible user-space regression.

So not that easy, sadly.

Cheers,

Hannes
--
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer