Re: [Xen-devel] [PATCH v3 07/10] xen/nodemask: Drop nodes_{setall, clear}() and improve the initialisers

[Jan Beulich <JBeulich@xxxxxxxx>]

On 29.07.2019 14:12, Andrew Cooper wrote:
> There is no need to use runtime variable-length clearing when MAX_NUMNODES is
> known to the compiler.  Drop these functions and use the initialisers instead.

The only slight concern I have with this is that it further locks
down the maximum remaining to be a compile time constant. But this
is not an objection, just a remark.

> @@ -67,7 +65,34 @@ typedef struct { DECLARE_BITMAP(bits, MAX_NUMNODES); } 
> nodemask_t;
>   
>   #define nodemask_bits(src) ((src)->bits)
>   
> -extern nodemask_t _unused_nodemask_arg_;
> +#define NODEMASK_LAST_WORD BITMAP_LAST_WORD_MASK(MAX_NUMNODES)
> +
> +#define NODEMASK_NONE                                                   \
> +((nodemask_t) {{                                                        \
> +        [0 ... BITS_TO_LONGS(MAX_NUMNODES) - 1] = 0                     \
> +}})
> +
> +#if MAX_NUMNODES <= BITS_PER_LONG
> +
> +#define NODEMASK_ALL      ((nodemask_t) {{ NODEMASK_LAST_WORD }})
> +#define NODEMASK_OF(node) ((nodemask_t) {{ 1UL << (node) }})
> +
> +#else /* MAX_NUMNODES > BITS_PER_LONG */
> +
> +#define NODEMASK_ALL                                                    \
> +((nodemask_t) {{                                                        \
> +        [0 ... BITS_TO_LONGS(MAX_NUMNODES) - 2] = ~0UL,                 \
> +        [BITS_TO_LONGS(MAX_NUMNODES) - 1] = NODEMASK_LAST_WORD          \
> +}})
> +
> +#define NODEMASK_OF(node)                                               \
> +({                                                                      \
> +    nodemask_t m = NODES_NONE;                                          \
> +    m.bits[(node) / BITS_PER_LONG] = 1UL << ((node) % BITS_PER_LONG);   \

I think you will want to avoid the double evaluation of "node"
here. With this taken care of
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan
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