15/02/2024 07:21, Tyler Retzlaff:
> Provide a macro that allows conditional expansion of RTE_MARKER fields
> to empty to allow rte_mbuf to be used with MSVC. It is proposed that
> we announce the fields to be __rte_deprecated (currently disabled).
>
> Introduce C11 anonymous unions to permit aliasing of well-known
> offsets by name into the rte_mbuf structure by a *new* name and to
> provide padding for cache alignment.
>
> Signed-off-by: Tyler Retzlaff <roret...@linux.microsoft.com>
> ---
> doc/guides/rel_notes/deprecation.rst | 20 ++
> lib/eal/include/rte_common.h | 6 +
> lib/mbuf/rte_mbuf_core.h | 375
> +++++++++++++++++++----------------
> 3 files changed, 233 insertions(+), 168 deletions(-)
>
> diff --git a/doc/guides/rel_notes/deprecation.rst
> b/doc/guides/rel_notes/deprecation.rst
> index 10630ba..8594255 100644
> --- a/doc/guides/rel_notes/deprecation.rst
> +++ b/doc/guides/rel_notes/deprecation.rst
> @@ -17,6 +17,26 @@ Other API and ABI deprecation notices are to be posted
> below.
> Deprecation Notices
> -------------------
>
> +* mbuf: Named zero sized fields of type ``RTE_MARKER`` and ``RTE_MARKER64``
> + will be removed from ``struct rte_mbuf`` and replaced with new fields
> + in anonymous unions.
> +
> + The names of the fields impacted are:
> +
> + old name new name
> +
> + ``cacheline0`` ``mbuf_cachelin0``
> + ``rearm_data`` ``mbuf_rearm_data``
> + ``rx_descriptor_fields1`` ``mbuf_rx_descriptor_fields1``
> + ``cacheline1`` ``mbuf_cachelin1``
> +
> + Contributions to DPDK should immediately start using the new names,
> + applications should adapt to new names as soon as possible as the
> + old names will be removed in a future DPDK release.
> +
> + Note: types of the new names are not API compatible with the old and
> + some code conversion is required to maintain correct behavior.
> +
> * build: The ``enable_kmods`` option is deprecated and will be removed in a
> future release.
> Setting/clearing the option has no impact on the build.
> Instead, kernel modules will be always built for OS's where out-of-tree
> kernel modules
> diff --git a/lib/eal/include/rte_common.h b/lib/eal/include/rte_common.h
> index d7d6390..af73f67 100644
> --- a/lib/eal/include/rte_common.h
> +++ b/lib/eal/include/rte_common.h
> @@ -582,6 +582,12 @@ static void __attribute__((destructor(RTE_PRIO(prio)),
> used)) func(void)
> /** Marker for 8B alignment in a structure. */
> __extension__ typedef uint64_t RTE_MARKER64[0];
>
> +#define __rte_marker(type, name) type name /* __rte_deprecated */
> +
> +#else
> +
> +#define __rte_marker(type, name)
> +
> #endif
>
> /*********** Macros for calculating min and max **********/
> diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h
> index 5688683..9e9590b 100644
> --- a/lib/mbuf/rte_mbuf_core.h
> +++ b/lib/mbuf/rte_mbuf_core.h
> @@ -16,7 +16,10 @@
> * New fields and flags should fit in the "dynamic space".
> */
>
> +#include <assert.h>
> +#include <stdalign.h>
> #include <stdint.h>
> +#include <stddef.h>
>
> #include <rte_byteorder.h>
> #include <rte_stdatomic.h>
> @@ -464,204 +467,240 @@ enum {
> * The generic rte_mbuf, containing a packet mbuf.
> */
> struct rte_mbuf {
> - RTE_MARKER cacheline0;
> -
> - void *buf_addr; /**< Virtual address of segment buffer. */
> + __rte_marker(RTE_MARKER, cacheline0);
You don't need to keep the first argument.
This would be simpler:
__rte_marker(cacheline0);
You just need to create 2 functions: __rte_marker and __rte_marker64.
You should replace all occurrences of RTE_MARKER in DPDK in one patch,
and mark RTE_MARKER as deprecated (use #pragma GCC poison)
> + union {
> + char mbuf_cacheline0[RTE_CACHE_LINE_MIN_SIZE];
> + __extension__
> + struct {
> + void *buf_addr; /**< Virtual address of
> segment buffer.
I think it is ugly.
Changing mbuf API is a serious issue.
