On 3/26/2026 6:24 PM, David Marchand wrote:
> Some applications use port hotplug as their primary way for using DPDK
> resources.
> Having a systematic device probing is a problem when not all available
> resources will be used by the application, as such applications won't set
> an explicit allow list at startup.
>
> This is the case for OVS on systems with multiple mlx5 devices:
> one device can be used by the kernel while the other(s) are used by DPDK.
> In such a setup, the kernel used device may get reconfigured in
> unexpected ways and trigger issues like the one described by Kevin
> not so long ago in bugzilla 1873.
>
> Add an EAL option so that we can change the default behavior from
> block-listing to allow-listing which can be summed up as disabling
> automatic probing.
> In case some applications want to require automatic probing, add the
> opposite option.
>
> Signed-off-by: David Marchand <[email protected]>
> Acked-by: Bruce Richardson <[email protected]>
> Reviewed-by: Robin Jarry <[email protected]>
> Acked-by: Hemant Agrawal <[email protected]>
> Tested-by: Maxime Leroy <[email protected]>
> Acked-by: Kevin Traynor <[email protected]>
> ---
> Changes since RFC v2:
> - added -A short option alias as it seems intuitive to use with -a,
> - renamed option to --no-auto-probing (half Robin and half Thomas
> suggestions),
> - made -A and -b conflicting options,
> - added opposite option in case an application wants an explicit behavior,
> - updated unit tests accordingly,
> - updated documentation (namely some detail on --vdev),
>
> Changes since RFC v1:
> - changed approach following Bruce suggestion,
>
> ---
> app/test/test_eal_flags.c | 63 +++++++++++++++++++++++
> devtools/test-null.sh | 2 +-
> doc/guides/linux_gsg/eal_args.include.rst | 13 +++++
> lib/eal/common/eal_common_bus.c | 17 +++---
> lib/eal/common/eal_common_options.c | 10 ++++
> lib/eal/common/eal_internal_cfg.h | 1 +
> lib/eal/common/eal_option_list.h | 2 +
> 7 files changed, 101 insertions(+), 7 deletions(-)
>
> diff --git a/app/test/test_eal_flags.c b/app/test/test_eal_flags.c
> index b3a8d0ae6f..5594cc992d 100644
> --- a/app/test/test_eal_flags.c
> +++ b/app/test/test_eal_flags.c
> @@ -119,6 +119,8 @@ test_misc_flags(void)
> #define no_hpet "--no-hpet"
> #define no_huge "--no-huge"
> #define no_shconf "--no-shconf"
> +#define auto_probing "--auto-probing"
> +#define no_auto_probing "--no-auto-probing"
> #define allow "--allow"
> #define vdev "--vdev"
> #define no_pci "--no-pci"
> @@ -338,6 +340,14 @@ test_allow_flag(void)
> allow, "09:0B.3,type=test",
> allow, "08:00.1,type=normal",
> };
> + const char *wlval4[] = {prgname, prefix, mp_flag, eal_debug_logs,
> + no_auto_probing };
> + const char *wlval5[] = {prgname, prefix, mp_flag, eal_debug_logs,
> + no_auto_probing, allow, "00FF:09:0B.3"};
> + const char *wlval6[] = {prgname, prefix, mp_flag, eal_debug_logs,
> + auto_probing };
> + const char *wlval7[] = {prgname, prefix, mp_flag, eal_debug_logs,
> + auto_probing, allow, "00FF:09:0B.3"};
>
> for (i = 0; i < RTE_DIM(wlinval); i++) {
> if (launch_proc(wlinval[i]) == 0) {
> @@ -360,6 +370,26 @@ test_allow_flag(void)
> __LINE__);
> return -1;
> }
> + if (launch_proc(wlval4) != 0) {
> + printf("Error (line %d) - process did not run ok with
> no-auto-probing\n",
> + __LINE__);
> + return -1;
> + }
> + if (launch_proc(wlval5) != 0) {
> + printf("Error (line %d) - process did not run ok with
> no-auto-probing + allow\n",
> + __LINE__);
> + return -1;
> + }
> + if (launch_proc(wlval6) != 0) {
> + printf("Error (line %d) - process did not run ok with
> auto-probing\n",
> + __LINE__);
> + return -1;
> + }
> + if (launch_proc(wlval7) != 0) {
> + printf("Error (line %d) - process did not run ok with
> auto-probing + allow\n",
> + __LINE__);
> + return -1;
> + }
>
> return 0;
> }
> @@ -383,6 +413,11 @@ test_invalid_b_flag(void)
> {prgname, prefix, mp_flag, eal_debug_logs, "-b",
> "error0:0:0.1"},
> {prgname, prefix, mp_flag, eal_debug_logs, "-b", "0:0:0.1.2"},
> };
> + const char *blinval_probing[] =
> + {prgname, prefix, mp_flag, eal_debug_logs, "-b", "0:0.0",
> auto_probing};
> + const char *blinval_probing_inval[] =
> + {prgname, prefix, mp_flag, eal_debug_logs, "-b", "0:0.0",
> no_auto_probing};
> +
> /* Test with valid blocklist option */
> const char *blval[] = {prgname, prefix, mp_flag, eal_debug_logs,
> "-b", "FF:09:0B.3"};
> @@ -396,6 +431,16 @@ test_invalid_b_flag(void)
> return -1;
> }
> }
> + if (launch_proc(blinval_probing) != 0) {
> + printf("Error (line %d) - process did not run ok with blocklist
> and auto-probing\n",
> + __LINE__);
> + return -1;
> + }
> + if (launch_proc(blinval_probing_inval) == 0) {
> + printf("Error (line %d) - process did run ok with blocklist and
> no-auto-probing\n",
> + __LINE__);
> + return -1;
> + }
> if (launch_proc(blval) != 0) {
> printf("Error (line %d) - process did not run ok with valid
> blocklist value\n",
> __LINE__);
> @@ -434,6 +479,12 @@ test_invalid_vdev_flag(void)
> const char *vdevval3[] = {prgname, prefix, no_huge, eal_debug_logs,
> bus_debug_logs, no_pci, vdev,
> "net_ring0,nodeaction=r1:0:CREATE"};
>
> + const char *vdevval4[] = {prgname, prefix, no_huge, eal_debug_logs,
> + bus_debug_logs, no_auto_probing, vdev,
> "net_ring0"};
> +
> + const char *vdevval5[] = {prgname, prefix, no_huge, eal_debug_logs,
> + bus_debug_logs, auto_probing, vdev,
> "net_ring0"};
> +
> if (launch_proc(vdevinval) == 0) {
> printf("Error (line %d) - process did run ok with invalid vdev
> parameter\n",
> __LINE__);
> @@ -457,6 +508,18 @@ test_invalid_vdev_flag(void)
> __LINE__);
> return -1;
> }
> +
> + if (launch_proc(vdevval4) != 0) {
> + printf("Error (line %d) - process did not run ok with valid
> vdev value and no-auto-probing\n",
> + __LINE__);
> + return -1;
> + }
> +
> + if (launch_proc(vdevval5) != 0) {
> + printf("Error (line %d) - process did not run ok with valid
> vdev value and auto-probing\n",
> + __LINE__);
> + return -1;
> + }
> return 0;
> #else
> return TEST_SKIPPED;
> diff --git a/devtools/test-null.sh b/devtools/test-null.sh
> index 8f21189262..5e8a1b20cd 100755
> --- a/devtools/test-null.sh
> +++ b/devtools/test-null.sh
> @@ -30,7 +30,7 @@ logfile=$build/test-null.log
> (sleep 1 && echo stop) |
> # testpmd only needs 20M, make it x2 (default number of cores) for NUMA
> systems
> $testpmd -l $corelist --no-huge -m 40 \
> - $libs -a 0:0.0 --vdev net_null1 --vdev net_null2 $eal_options -- \
> + $libs -A --vdev net_null1 --vdev net_null2 $eal_options -- \
> --no-mlockall --total-num-mbufs=2048 $testpmd_options -ia | tee $logfile
>
> # we expect two ports and some traffic is received and transmitted
> diff --git a/doc/guides/linux_gsg/eal_args.include.rst
> b/doc/guides/linux_gsg/eal_args.include.rst
> index 4a3c4d9b5f..db9eff9321 100644
> --- a/doc/guides/linux_gsg/eal_args.include.rst
> +++ b/doc/guides/linux_gsg/eal_args.include.rst
> @@ -101,6 +101,19 @@ Lcore-related options
> Device-related options
> ~~~~~~~~~~~~~~~~~~~~~~
>
> +* ``-A, --no-auto-probing``
> +
> + By default, EAL probes all devices on every available bus, unless some
> ``-a``/``-b``
> + options are passed.
> + Disable automatic probing of non-blocked devices.
> +
> +.. Note::
> + Block list cannot be used when auto probing is disabled.
> +
> + On the other hand, disabling auto probing does not affect the VDEV bus.
> + The VDEV bus is not concerned by automatic probing and requires explicit
> + ``-a`` or ``--vdev``.
> +
> * ``-b, --block <[domain:]bus:devid.func>``
>
> Skip probing a PCI device to prevent EAL from using it.
> diff --git a/lib/eal/common/eal_common_bus.c b/lib/eal/common/eal_common_bus.c
> index 2ca0af7914..47ba303468 100644
> --- a/lib/eal/common/eal_common_bus.c
> +++ b/lib/eal/common/eal_common_bus.c
> @@ -250,18 +250,23 @@ RTE_EXPORT_INTERNAL_SYMBOL(rte_bus_is_ignored_device)
> bool
> rte_bus_is_ignored_device(const struct rte_bus *bus, const char *dev_name)
> {
> + const struct internal_config *internal_conf =
> eal_get_internal_configuration();
> struct rte_devargs *devargs = rte_bus_find_devargs(bus, dev_name);
> + enum rte_bus_scan_mode scan_mode = bus->conf.scan_mode;
>
> - switch (bus->conf.scan_mode) {
> - case RTE_BUS_SCAN_ALLOWLIST:
> + if (scan_mode == RTE_BUS_SCAN_UNDEFINED) {
> + if (internal_conf->no_auto_probing != 0)
> + scan_mode = RTE_BUS_SCAN_ALLOWLIST;
> + else
> + scan_mode = RTE_BUS_SCAN_BLOCKLIST;
> + }
> +
> + if (scan_mode == RTE_BUS_SCAN_ALLOWLIST) {
> if (devargs && devargs->policy == RTE_DEV_ALLOWED)
> return false;
> - break;
> - case RTE_BUS_SCAN_UNDEFINED:
> - case RTE_BUS_SCAN_BLOCKLIST:
> + } else {
> if (devargs == NULL || devargs->policy != RTE_DEV_BLOCKED)
> return false;
> - break;
> }
> return true;
> }
> diff --git a/lib/eal/common/eal_common_options.c
> b/lib/eal/common/eal_common_options.c
> index aad676a004..290386dc63 100644
> --- a/lib/eal/common/eal_common_options.c
> +++ b/lib/eal/common/eal_common_options.c
> @@ -233,10 +233,15 @@ eal_collate_args(int argc, char **argv)
> EAL_LOG(ERR, "Options allow (-a) and block (-b) can't be used
> at the same time");
> return -1;
> }
> + if (args.no_auto_probing && !TAILQ_EMPTY(&args.block)) {
> + EAL_LOG(ERR, "Options no-auto-probing and block (-b) can't be
> used at the same time");
> + return -1;
> + }
>
> /* for non-list args, we can just check for zero/null values using
> macro */
> if (CONFLICTING_OPTIONS(args, coremask, lcores) ||
> CONFLICTING_OPTIONS(args, service_coremask,
> service_corelist) ||
> + CONFLICTING_OPTIONS(args, no_auto_probing,
> auto_probing) ||
> CONFLICTING_OPTIONS(args, no_telemetry, telemetry) ||
> CONFLICTING_OPTIONS(args, memory_size, numa_mem) ||
> CONFLICTING_OPTIONS(args, no_huge, numa_mem) ||
> @@ -518,6 +523,8 @@ eal_reset_internal_config(struct internal_config
> *internal_cfg)
> memset(internal_cfg->vfio_vf_token, 0,
> sizeof(internal_cfg->vfio_vf_token));
>
> + internal_cfg->no_auto_probing = 0;
> +
> #ifdef RTE_LIBEAL_USE_HPET
> internal_cfg->no_hpet = 0;
> #else
> @@ -1972,6 +1979,9 @@ eal_parse_args(void)
> }
> }
>
> + if (args.no_auto_probing)
> + int_cfg->no_auto_probing = 1;
> +
> /* device -a/-b/-vdev options*/
> TAILQ_FOREACH(arg, &args.allow, next)
> if (eal_option_device_add(RTE_DEVTYPE_ALLOWED, arg->arg) < 0)
> diff --git a/lib/eal/common/eal_internal_cfg.h
> b/lib/eal/common/eal_internal_cfg.h
> index 95d327a613..fac45cbe66 100644
> --- a/lib/eal/common/eal_internal_cfg.h
> +++ b/lib/eal/common/eal_internal_cfg.h
> @@ -104,6 +104,7 @@ struct internal_config {
> struct simd_bitwidth max_simd_bitwidth;
> /**< max simd bitwidth path to use */
> size_t huge_worker_stack_size; /**< worker thread stack size */
> + unsigned int no_auto_probing; /**< true to switch from block-listing to
> allow-listing */
> };
>
> void eal_reset_internal_config(struct internal_config *internal_cfg);
> diff --git a/lib/eal/common/eal_option_list.h
> b/lib/eal/common/eal_option_list.h
> index abee16340b..6a5ddfd8d1 100644
> --- a/lib/eal/common/eal_option_list.h
> +++ b/lib/eal/common/eal_option_list.h
> @@ -32,6 +32,7 @@
> * Format of each entry: long name, short name, help string, struct member
> name.
> */
> /* (Alphabetical) List of common options first */
> +BOOL_ARG("--auto-probing", NULL, "Let EAL probe all available devices unless
> some -a/-b option is set.", auto_probing)
This commit only check auto_probing and no_auto_probing conflict,
I think it no need add this arg because auto-probing is default behavir when
-a/-b not exist.
> LIST_ARG("--allow", "-a", "Add device to allow-list, causing DPDK to only
> use specified devices", allow)
> STR_ARG("--base-virtaddr", NULL, "Base virtual address to reserve memory",
> base_virtaddr)
> LIST_ARG("--block", "-b", "Add device to block-list, preventing DPDK from
> using the device", block)
> @@ -51,6 +52,7 @@ STR_ARG("--mbuf-pool-ops-name", NULL, "User defined mbuf
> default pool ops name",
> STR_ARG("--memory-channels", "-n", "Number of memory channels per socket",
> memory_channels)
> STR_ARG("--memory-ranks", "-r", "Force number of memory ranks (don't
> detect)", memory_ranks)
> STR_ARG("--memory-size", "-m", "Total size of memory to allocate initially",
> memory_size)
> +BOOL_ARG("--no-auto-probing", "-A", "Do not probe any devices unless some -a
> option is set", no_auto_probing)
> BOOL_ARG("--no-hpet", NULL, "Disable HPET timer", no_hpet)
> BOOL_ARG("--no-huge", NULL, "Disable hugetlbfs support", no_huge)
> BOOL_ARG("--no-pci", NULL, "Disable all PCI devices", no_pci)
