Re: [PATCH v2 7/7] eal: configure initial device probing

[fengchengwen <fengchengwen@huawei.com>]

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 <david.marchand@redhat.com>
> Acked-by: Bruce Richardson <bruce.richardson@intel.com>
> Reviewed-by: Robin Jarry <rjarry@redhat.com>
> Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>
> Tested-by: Maxime Leroy <maxime@leroys.fr>
> Acked-by: Kevin Traynor <ktraynor@redhat.com>
> ---
> 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)