Re: [PATCH 4/5] xen/xsm: Improve fallback handling in xsm_fixup_ops()

["Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>]

On 11/5/21 9:55 AM, Andrew Cooper wrote:
> The current xsm_fixup_ops() is just shy of a full page when compiled, and very
> fragile to NULL function pointer errors.
>
> Address both of these issues with a minor piece of structure (ab)use.
> Introduce dummy_ops, and fixup the provided xsm_ops pointer by treating both
> as an array of unsigned longs.
>
> The compiled size improvement speaks for itself:
>
>    $ ../scripts/bloat-o-meter xen-syms-before xen-syms-after
>    add/remove: 1/0 grow/shrink: 0/1 up/down: 712/-3897 (-3185)
>    Function                                     old     new   delta
>    dummy_ops                                      -     712    +712
>    xsm_fixup_ops                               3987      90   -3897
>
> and there is an additional safety check that will make it obvious during
> development if there is an issue with the fallback handling.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
> CC: Daniel Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>

Reviewed-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>