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Re: [Qemu-devel] [PATCH for-2.11 2/6] ppc: make cpu_model translation to


From: David Gibson
Subject: Re: [Qemu-devel] [PATCH for-2.11 2/6] ppc: make cpu_model translation to type consistent
Date: Fri, 25 Aug 2017 19:45:38 +1000
User-agent: Mutt/1.8.3 (2017-05-23)

On Fri, Aug 25, 2017 at 09:27:40AM +0200, Igor Mammedov wrote:
> On Fri, 25 Aug 2017 11:38:19 +1000
> David Gibson <address@hidden> wrote:
> 
> > On Thu, Aug 24, 2017 at 10:21:47AM +0200, Igor Mammedov wrote:
> > > PPC handles -cpu FOO rather incosistently,
> > > i.e. it does case-insensitive matching of FOO to
> > > a CPU type (see: ppc_cpu_compare_class_name) but
> > > handles alias names as case-sensitive, as result:
> > > 
> > >  # qemu-system-ppc64 -M mac99 -cpu g3
> > >  qemu-system-ppc64: unable to find CPU model ' kN�U'
> > > 
> > >  # qemu-system-ppc64 -cpu 970MP_V1.1
> > >  qemu-system-ppc64: Unable to find sPAPR CPU Core definition
> > > 
> > > while
> > > 
> > >  # qemu-system-ppc64 -M mac99 -cpu G3
> > >  # qemu-system-ppc64 -cpu 970MP_v1.1
> > > 
> > > start up just fine.
> > > 
> > > Considering we can't take case-insensitive matching away,
> > > make it case-insensitive for  all alias/type/core_type
> > > lookups.
> > > 
> > > As side effect it allows to remove duplicate core types
> > > which are the same but use lower-case letters in name.
> > > 
> > > Signed-off-by: Igor Mammedov <address@hidden>  
> > 
> > Hmm.  So, I'm certainly good with making the matching more consistent,
> > and removing extra entries differing only in case.
> > 
> > However, I don't like capitalizing everything in the model table.  The
> > "canonical" capitalization - as in how it appears in manuals and
> > marketing info - is quite frequently mixed case.  So I think making
> > everything caps in the table will make it harder to read in the
> > context of looking at the corresponding documentation.
> only cpu models => typenames are made caps, the rest

Yes, I know.  A number of the CPU model names themselves have mixed
case.  Really.

> incl. description is kept as is in mixed case.
> It looks like _desc is the thing one would use for
> 1:1 lookup in spec, while _name isn't direct match consistently
> (i.e. sometimes it skips spaces and sometimes spaces are replaced by 
> underscore).
> So keeping _name in mixed case unnecessarily complicates name->type lookup.
> 
> These mixed case + case-insensitive is what made lookup
> code over-engineered and overly complex.

I'm fine with making all the lookups case insensitive.  I just don't
want to drop the case on the names in the actual code.

> As result it evolved (regressed) to inconsistent name handling
> since it's rather hard to understand what's going on there.

Yeah, I know :/.

> > Can we instead retain mixed case in the table, and capitalize both
> > sides at the comparison time?
> it has to be the same-case since PPC has case-insensitive cpu_model
> matching (sometimes :/). Normalized /same case/ typenames
> are necessary for object_class_by_name() to work as it does exact match.
> So it would be possible to replace custom fetching of CPU types
> and iterating over it with custom comparator with object_class_by_name().
> As it's done in 4/6.
> This patch and 3/6 are only preparatory patches for 4/6.

Ah.  Hrm.  That's awkward.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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