Re: [Xen-devel] [PATCH-for-4.13 v5] Rationalize max_grant_frames and max_maptrack_frames handling

["Durrant, Paul" <pdurrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Ian Jackson <ian.jackson@xxxxxxxxxx>
> Sent: 29 November 2019 15:47
> To: Wei Liu <wl@xxxxxxx>
> Cc: Durrant, Paul <pdurrant@xxxxxxxxxx>; Anthony Perard
> <anthony.perard@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx; George Dunlap
> <George.Dunlap@xxxxxxxxxx>; Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Jan
> Beulich <jbeulich@xxxxxxxx>; Julien Grall <julien@xxxxxxx>; Konrad
> Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>; Stefano Stabellini
> <sstabellini@xxxxxxxxxx>; Marek Marczykowski-Górecki
> <marmarek@xxxxxxxxxxxxxxxxxxxxxx>; Volodymyr Babchuk
> <Volodymyr_Babchuk@xxxxxxxx>; Roger Pau Monne <roger.pau@xxxxxxxxxx>
> Subject: Re: [PATCH-for-4.13 v5] Rationalize max_grant_frames and
> max_maptrack_frames handling
> 
> Wei Liu writes ("Re: [PATCH-for-4.13 v5] Rationalize max_grant_frames and
> max_maptrack_frames handling"):
> > What if we use 0xffffffff to denote default instead? That wouldn't
> > require changing the type here.
> 
> Is there some reason we wouldn't use ~0 to mean default ?
> 
> In the tools area we normally spell this as
>      ~(some appropriate type)0
> to make sure it has the right width.  But if we know the type and it
> is of fixed length, as here, 0xffffffffu is OK too.
> 
> > The type change here makes me feel a bit uncomfortable, though in
> > practice it may not matter. I don't see anyone would specify a value
> > that would become negative when cast from uint32 to integer.
> 
> The problem with the type change is that in principle we have to audit
> all the places the variables are used.
> 

Can a toolstack maintainer please come up with a concrete suggestion as to what 
the patch should do then? It's now at v6 and time is short.

  Paul

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