On Tue, Jul 08, 2025 at 02:28:16PM +0200, David Marchand wrote:
> Content (param[]) of received multiprocess messages are aligned with
> a 4 bytes constraint.
>
> Before patch:
> struct mp_msg_internal {
> int type; /* 0 4 */
> struct rte_mp_msg {
> char name[64]; /* 4 64 */
> /* --- cacheline 1 boundary (64 bytes) was 4 bytes ago --- */
> int len_param; /* 68 4 */
> int num_fds; /* 72 4 */
> /* typedef uint8_t -> __uint8_t */ unsigned char param[256]; /* 76 256 */
> /* --- cacheline 5 boundary (320 bytes) was 12 bytes ago --- */
> int fds[253]; /* 332 1012 */
> } msg; /* 4 1340 */
>
> /* size: 1344, cachelines: 21, members: 2 */
> };
>
> This results in many unaligned accesses for multiprocess malloc requests.
>
> Examples:
> ../lib/eal/common/malloc_mp.c:308:32: runtime error:
> member access within misaligned address 0x7f7b35df4684 for type
> 'const struct malloc_mp_req', which requires 8 byte alignment
>
> ../lib/eal/common/malloc_mp.c:158:9: runtime error:
> member access within misaligned address 0x7f36a535bb5c for type
> 'const struct malloc_mp_req', which requires 8 byte alignment
>
> ../lib/eal/common/malloc_mp.c:171:8: runtime error:
> member access within misaligned address 0x7f4ba65f296c for type
> 'struct malloc_mp_req', which requires 8 byte alignment
>
> Signed-off-by: David Marchand <david.march...@redhat.com>
> ---
> lib/eal/common/eal_common_proc.c | 2 +-
> lib/eal/common/malloc_mp.c | 18 +++++++++---------
> 2 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/lib/eal/common/eal_common_proc.c
> b/lib/eal/common/eal_common_proc.c
> index 0dea787e38..3846c7178d 100644
> --- a/lib/eal/common/eal_common_proc.c
> +++ b/lib/eal/common/eal_common_proc.c
> @@ -62,7 +62,7 @@ enum mp_type {
>
> struct mp_msg_internal {
> int type;
> - struct rte_mp_msg msg;
> + alignas(8) struct rte_mp_msg msg;
> };
>
> struct async_request_param {
> diff --git a/lib/eal/common/malloc_mp.c b/lib/eal/common/malloc_mp.c
> index 9765277f5d..000c7f6b47 100644
> --- a/lib/eal/common/malloc_mp.c
> +++ b/lib/eal/common/malloc_mp.c
> @@ -148,7 +148,7 @@ get_unique_id(void)
> static int
> handle_sync(const struct rte_mp_msg *msg, const void *peer)
> {
> - struct rte_mp_msg reply;
> + alignas(8) struct rte_mp_msg reply;
> const struct malloc_mp_req *req =
> (const struct malloc_mp_req *)msg->param;
This patch seems to have a lot of these definitions with alignas added to
them. Would it be simpler just to put the alignas inside the rte_mp_msg
definition?
More specifically, if its the "uint8_t param" element that needs alignment,
how about changing that specific field to make it aligned?
/Bruce
