Re: [PATCH] xen/include/public: add macro for invalid grant reference

[Juergen Gross <jgross@xxxxxxxx>]

On 21.02.22 15:18, Jan Beulich wrote:
> On 21.02.2022 13:42, Juergen Gross wrote:
> > Providing a macro for an invalid grant reference would be beneficial
> > for users, especially as some are using the wrong value "0" for that
> > purpose.
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> Over the years I've been considering to add such to the public
> interface, perhaps even more than once. But I'm afraid it's not that
> easy. In principle 0xffffffff (which btw isn't necessarily ~0u) could
I can change that to use 0xffffffff explicitly.

> be a valid ref. It is really internal agreement by users of the
> interface to set for themselves that they're not ever going to make
> a valid grant behind that reference.
As the grant reference is an index into the grant table this would
limit the size of the grant table to "only" UINT_MAX - 1. I don't
think this will be ever a concern (other than an academical one).


Juergen

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