On Wed, Feb 14, 2024 at 8:07 AM Tyler Retzlaff
<roret...@linux.microsoft.com> wrote:
>
> Remove explicit alignment with __rte_aligned(sizeof(T)) on buf_iova
> field in the absence of packing the field should be correctly aligned.
>
> Signed-off-by: Tyler Retzlaff <roret...@linux.microsoft.com>
> ---
> lib/mbuf/rte_mbuf_core.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h
> index 5688683..7369e3e 100644
> --- a/lib/mbuf/rte_mbuf_core.h
> +++ b/lib/mbuf/rte_mbuf_core.h
> @@ -463,7 +463,7 @@ enum {
> /**
> * The generic rte_mbuf, containing a packet mbuf.
> */
> -struct rte_mbuf {
> +struct __rte_cache_aligned rte_mbuf {
> RTE_MARKER cacheline0;
>
> void *buf_addr; /**< Virtual address of segment buffer. */
> @@ -476,7 +476,7 @@ struct rte_mbuf {
> * same mbuf cacheline0 layout for 32-bit and 64-bit. This makes
> * working on vector drivers easier.
> */
> - rte_iova_t buf_iova __rte_aligned(sizeof(rte_iova_t));
> + rte_iova_t buf_iova;
> #else
Before the change, for 32bits build:
struct rte_mbuf {
RTE_MARKER cacheline0; /* 0 0 */
void * buf_addr; /* 0 4 */
/* XXX 4 bytes hole, try to pack */
rte_iova_t buf_iova
__attribute__((__aligned__(8))); /* 8 8 */
RTE_MARKER64 rearm_data; /* 16 0 */
...
After the change:
struct rte_mbuf {
RTE_MARKER cacheline0; /* 0 0 */
void * buf_addr; /* 0 4 */
rte_iova_t buf_iova; /* 4 8 */
RTE_MARKER64 rearm_data; /* 12 0 */
...
So it looks like uint64_t is not naturally aligned on 8 bytes for x86
32 bits, which explains the current explicit constraint (and comment
in the header).
See also 586ec205bcbb ("mbuf: fix 64-bit address alignment in 32-bit builds").
This results in a cascading offset changes triggering multiple build
errors in vectorised code:
In file included from
../../../git/pub/dpdk.org/main/lib/eal/x86/include/rte_vect.h:16,
from
../../../git/pub/dpdk.org/main/drivers/common/idpf/idpf_common_rxtx_avx512.c:5:
../../../git/pub/dpdk.org/main/drivers/common/idpf/idpf_common_rxtx_avx512.c:
In function ‘idpf_singleq_rearm_common’:
../../../git/pub/dpdk.org/main/lib/eal/include/rte_common.h:509:55:
error: size of unnamed array is negative
509 | #define RTE_BUILD_BUG_ON(condition) ((void)sizeof(char[1 -
2*!!(condition)]))
| ^
../../../git/pub/dpdk.org/main/drivers/common/idpf/idpf_common_rxtx_avx512.c:68:17:
note: in expansion of macro ‘RTE_BUILD_BUG_ON’
68 | RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, buf_iova) !=
| ^~~~~~~~~~~~~~~~
../../../git/pub/dpdk.org/main/drivers/common/idpf/idpf_common_rxtx_avx512.c:
In function ‘_idpf_singleq_recv_raw_pkts_avx512’:
../../../git/pub/dpdk.org/main/lib/eal/include/rte_common.h:509:55:
error: size of unnamed array is negative
509 | #define RTE_BUILD_BUG_ON(condition) ((void)sizeof(char[1 -
2*!!(condition)]))
| ^
../../../git/pub/dpdk.org/main/drivers/common/idpf/idpf_common_rxtx_avx512.c:461:17:
note: in expansion of macro ‘RTE_BUILD_BUG_ON’
461 | RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf,
rearm_data) !=
| ^~~~~~~~~~~~~~~~
../../../git/pub/dpdk.org/main/drivers/common/idpf/idpf_common_rxtx_avx512.c:
In function ‘_idpf_splitq_recv_raw_pkts_avx512’:
../../../git/pub/dpdk.org/main/lib/eal/include/rte_common.h:509:55:
error: size of unnamed array is negative
509 | #define RTE_BUILD_BUG_ON(condition) ((void)sizeof(char[1 -
2*!!(condition)]))
| ^
../../../git/pub/dpdk.org/main/drivers/common/idpf/idpf_common_rxtx_avx512.c:921:17:
note: in expansion of macro ‘RTE_BUILD_BUG_ON’
921 | RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf,
rearm_data) !=
| ^~~~~~~~~~~~~~~~
--
David Marchand
