[PATCH v6 32/39] bpf: use C11 alignas

[Konstantin Ananyev]

> Subject: [PATCH v6 32/39] bpf: use C11 alignas
> 
> The current location used for __rte_aligned(a) for alignment of types
> and variables is not compatible with MSVC. There is only a single
> location accepted by both toolchains.
> 
> For variables standard C11 offers alignas(a) supported by conformant
> compilers i.e. both MSVC and GCC.
> 
> For types the standard offers no alignment facility that compatibly
> interoperates with C and C++ but may be achieved by relocating the
> placement of __rte_aligned(a) to the aforementioned location accepted
> by all currently supported toolchains.
> 
> To allow alignment for both compilers do the following:
> 
> * Move __rte_aligned from the end of {struct,union} definitions to
>   be between {struct,union} and tag.
> 
>   The placement between {struct,union} and the tag allows the desired
>   alignment to be imparted on the type regardless of the toolchain being
>   used for all of GCC, LLVM, MSVC compilers building both C and C++.
> 
> * Replace use of __rte_aligned(a) on variables/fields with alignas(a).
> 
> Signed-off-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
> Acked-by: Morten Brørup <mb at smartsharesystems.com>
> ---
>  lib/bpf/bpf_pkt.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/bpf/bpf_pkt.c b/lib/bpf/bpf_pkt.c
> index 793a75d..aaca935 100644
> --- a/lib/bpf/bpf_pkt.c
> +++ b/lib/bpf/bpf_pkt.c
> @@ -23,7 +23,7 @@
>   * information about installed BPF rx/tx callback
>   */
> 
> -struct bpf_eth_cbi {
> +struct __rte_cache_aligned bpf_eth_cbi {
>  	/* used by both data & control path */
>  	RTE_ATOMIC(uint32_t) use;    /*usage counter */
>  	const struct rte_eth_rxtx_callback *cb;  /* callback handle */
> @@ -33,7 +33,7 @@ struct bpf_eth_cbi {
>  	LIST_ENTRY(bpf_eth_cbi) link;
>  	uint16_t port;
>  	uint16_t queue;
> -} __rte_cache_aligned;
> +};
> 
>  /*
>   * Odd number means that callback is used by datapath.
> --

Acked-by: Konstantin Ananyev <konstantin.ananyev at huawei.com>
 

> 1.8.3.1