We've gone around in circles a little on this series. Let's discuss it
at the next techboard meeting, please put it on the agenda.
Summary
MSVC does not support the typedef of zero-sized typed arrays used in
struct rte_mbuf and a handful of other structs built on Windows. Better
known as ``RTE_MARKER`` fields.
There are two competing solutions we would like to know which to move
forward with.
1. Use C11 anonymous unions and anonymous struct extensions to replace
the RTE_MARKER fields which can maintain ABI and API compatibility.
2. Provide inline accessors for struct rte_mbuf for some fields and
removing others which maintains ABI but breaks API.
I'm proposing a mix of 1 & 2 to maintain ABI and some API for struct
rte_mbuf fields but remove (API breaking) cacheline{0,1} RTE_MARKER
fields in favor of existing inline functions for prefetching.
Thanks!
On Mon, Feb 26, 2024 at 09:41:18PM -0800, Tyler Retzlaff wrote:
> Collect duplicated RTE_BUILD_BUG_ON checks from drivers and place them
> at global scope with struct rte_mbuf definition using static_assert.
>
> Signed-off-by: Tyler Retzlaff <roret...@linux.microsoft.com>
> ---
> lib/mbuf/rte_mbuf_core.h | 34 ++++++++++++++++++++++++++++++++++
> 1 file changed, 34 insertions(+)
>
> diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h
> index 7000c04..36551c2 100644
> --- a/lib/mbuf/rte_mbuf_core.h
> +++ b/lib/mbuf/rte_mbuf_core.h
> @@ -16,8 +16,11 @@
> * New fields and flags should fit in the "dynamic space".
> */
>
> +#include <assert.h>
> +#include <stddef.h>
> #include <stdint.h>
>
> +#include <rte_common.h>
> #include <rte_byteorder.h>
> #include <rte_stdatomic.h>
>
> @@ -673,6 +676,37 @@ struct rte_mbuf {
> uint32_t dynfield1[9]; /**< Reserved for dynamic fields. */
> } __rte_cache_aligned;
>
> +static_assert(!(offsetof(struct rte_mbuf, ol_flags) !=
> + offsetof(struct rte_mbuf, rearm_data) + 8), "ol_flags");
> +static_assert(!(offsetof(struct rte_mbuf, rearm_data) !=
> + RTE_ALIGN(offsetof(struct rte_mbuf, rearm_data), 16)), "rearm_data");
> +static_assert(!(offsetof(struct rte_mbuf, data_off) !=
> + offsetof(struct rte_mbuf, rearm_data)), "data_off");
> +static_assert(!(offsetof(struct rte_mbuf, data_off) <
> + offsetof(struct rte_mbuf, rearm_data)), "data_off");
> +static_assert(!(offsetof(struct rte_mbuf, refcnt) <
> + offsetof(struct rte_mbuf, rearm_data)), "refcnt");
> +static_assert(!(offsetof(struct rte_mbuf, nb_segs) <
> + offsetof(struct rte_mbuf, rearm_data)), "nb_segs");
> +static_assert(!(offsetof(struct rte_mbuf, port) <
> + offsetof(struct rte_mbuf, rearm_data)), "port");
> +static_assert(!(offsetof(struct rte_mbuf, data_off) -
> + offsetof(struct rte_mbuf, rearm_data) > 6), "data_off");
> +static_assert(!(offsetof(struct rte_mbuf, refcnt) -
> + offsetof(struct rte_mbuf, rearm_data) > 6), "refcnt");
> +static_assert(!(offsetof(struct rte_mbuf, nb_segs) -
> + offsetof(struct rte_mbuf, rearm_data) > 6), "nb_segs");
> +static_assert(!(offsetof(struct rte_mbuf, port) -
> + offsetof(struct rte_mbuf, rearm_data) > 6), "port");
> +static_assert(!(offsetof(struct rte_mbuf, pkt_len) !=
> + offsetof(struct rte_mbuf, rx_descriptor_fields1) + 4), "pkt_len");
> +static_assert(!(offsetof(struct rte_mbuf, data_len) !=
> + offsetof(struct rte_mbuf, rx_descriptor_fields1) + 8), "data_len");
> +static_assert(!(offsetof(struct rte_mbuf, vlan_tci) !=
> + offsetof(struct rte_mbuf, rx_descriptor_fields1) + 10), "vlan_tci");
> +static_assert(!(offsetof(struct rte_mbuf, hash) !=
> + offsetof(struct rte_mbuf, rx_descriptor_fields1) + 12), "hash");
> +
> /**
> * Function typedef of callback to free externally attached buffer.
> */
> --
> 1.8.3.1
