[PATCH 2/2] eal: add meson options for hotplug MP message buffer sizes

[Long Li]

Add meson build options to allow increasing the multi-process hotplug
message buffer limits at build time for deployments with many NICs:
- 'dev_mp_devargs_max_len' (default 128): max device args length
- 'mp_max_param_len' (default 256): max MP IPC message param length

Example: meson setup build -Ddev_mp_devargs_max_len=256 -Dmp_max_param_len=512

Guard the existing #defines with #ifndef so the meson-generated values
from rte_build_config.h take precedence when overridden.

Add a static_assert to ensure eal_dev_mp_req fits within the MP message
param buffer, catching misconfiguration at compile time.

Note: all primary and secondary processes must be built with the same
values, as these sizes affect shared IPC message struct layouts.

Signed-off-by: Long Li <longli at microsoft.com>
---
 config/meson.build          | 2 ++
 lib/eal/common/hotplug_mp.h | 6 ++++++
 lib/eal/include/rte_eal.h   | 2 ++
 meson_options.txt           | 4 ++++
 4 files changed, 14 insertions(+)

diff --git a/config/meson.build b/config/meson.build
index 9ba7b9a338..d0c117dbc9 100644
--- a/config/meson.build
+++ b/config/meson.build
@@ -385,6 +385,8 @@ dpdk_conf.set('RTE_LIBEAL_USE_HPET', get_option('use_hpet'))
 dpdk_conf.set('RTE_ENABLE_STDATOMIC', get_option('enable_stdatomic'))
 dpdk_conf.set('RTE_ENABLE_TRACE_FP', get_option('enable_trace_fp'))
 dpdk_conf.set('RTE_PKTMBUF_HEADROOM', get_option('pkt_mbuf_headroom'))
+dpdk_conf.set('RTE_MP_MAX_PARAM_LEN', get_option('mp_max_param_len'))
+dpdk_conf.set('EAL_DEV_MP_DEV_ARGS_MAX_LEN', get_option('dev_mp_devargs_max_len'))
 # values which have defaults which may be overridden
 dpdk_conf.set('RTE_MAX_VFIO_GROUPS', 64)
 dpdk_conf.set('RTE_DRIVER_MEMPOOL_BUCKET_SIZE_KB', 64)
diff --git a/lib/eal/common/hotplug_mp.h b/lib/eal/common/hotplug_mp.h
index 7221284286..df8f987ea6 100644
--- a/lib/eal/common/hotplug_mp.h
+++ b/lib/eal/common/hotplug_mp.h
@@ -6,13 +6,16 @@
 #define _HOTPLUG_MP_H_
 
 #include "rte_dev.h"
+#include "rte_eal.h"
 
 #define EAL_DEV_MP_ACTION_REQUEST      "eal_dev_mp_request"
 #define EAL_DEV_MP_ACTION_RESPONSE     "eal_dev_mp_response"
 
 #define EAL_DEV_MP_DEV_NAME_MAX_LEN RTE_DEV_NAME_MAX_LEN
 #define EAL_DEV_MP_BUS_NAME_MAX_LEN 32
+#ifndef EAL_DEV_MP_DEV_ARGS_MAX_LEN
 #define EAL_DEV_MP_DEV_ARGS_MAX_LEN 128
+#endif
 
 enum eal_dev_req_type {
 	EAL_DEV_REQ_TYPE_ATTACH,
@@ -27,6 +30,9 @@ struct eal_dev_mp_req {
 	int result;
 };
 
+static_assert(sizeof(struct eal_dev_mp_req) <= RTE_MP_MAX_PARAM_LEN,
+	"eal_dev_mp_req exceeds RTE_MP_MAX_PARAM_LEN, increase mp_max_param_len");
+
 /**
  * Register all mp action callbacks for hotplug.
  *
diff --git a/lib/eal/include/rte_eal.h b/lib/eal/include/rte_eal.h
index 7241f3be5d..aef431a88a 100644
--- a/lib/eal/include/rte_eal.h
+++ b/lib/eal/include/rte_eal.h
@@ -158,7 +158,9 @@ bool rte_mp_disable(void);
 
 #define RTE_MP_MAX_FD_NUM	253  /* The max amount of fds (see SCM_MAX_FD) */
 #define RTE_MP_MAX_NAME_LEN	64   /* The max length of action name */
+#ifndef RTE_MP_MAX_PARAM_LEN
 #define RTE_MP_MAX_PARAM_LEN	256  /* The max length of param */
+#endif
 struct rte_mp_msg {
 	char name[RTE_MP_MAX_NAME_LEN];
 	int len_param;
diff --git a/meson_options.txt b/meson_options.txt
index e28d24054c..c6d07a3308 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -48,6 +48,10 @@ option('mbuf_refcnt_atomic', type: 'boolean', value: true, description:
        'Atomically access the mbuf refcnt.')
 option('platform', type: 'string', value: 'native', description:
        'Platform to build, either "native", "generic" or a SoC. Please refer to the Linux build guide for more information.')
+option('mp_max_param_len', type: 'integer', value: 256, description:
+       'Maximum length of parameters in multi-process IPC messages.')
+option('dev_mp_devargs_max_len', type: 'integer', value: 128, description:
+       'Maximum length of device arguments in multi-process hotplug messages.')
 option('pkt_mbuf_headroom', type: 'integer', value: 128, description:
        'Default data offset (in bytes) in a packet buffer to leave room for additional headers.')
 option('enable_stdatomic', type: 'boolean', value: false, description:
-- 
2.43.0