Re: [PATCH] net/intel/e1000: reduce the optimization level for gcc > 11

[Thierry Herbelot <thierry.herbelot@6wind.com>]

On 10/6/25 14:55, David Marchand wrote:
> On Mon, 6 Oct 2025 at 14:45, Thierry Herbelot
> <thierry.herbelot@6wind.com> wrote:
>>
>> The e1000 PMD stopped working under Ubuntu-24.04 (using gcc-13) when
>> compiled with -O3 (default level for all DPDK code). There is a crash
>> when starting testpmd:
>>
>> (gdb) bt
>> #0  rte_read32_relaxed (addr=0x1100800e00) at ../sources/lib/eal/include/generic/rte_io.h:290
>> #1  rte_read32 (addr=0x1100800e00) at ../sources/lib/eal/include/generic/rte_io.h:345
>> #2  e1000_read_addr (addr=0x1100800e00) at ../sources/drivers/net/intel/e1000/base/e1000_osdep.h:106
>> #3  e1000_id_led_init_generic (hw=0x1586788c0) at ../sources/drivers/net/intel/e1000/base/e1000_mac.c:1844
>> #4  0x000062aaf653c85f in e1000_init_hw_82540 (hw=0x1586788c0)
>>      at ../sources/drivers/net/intel/e1000/base/e1000_82540.c:308
>> #5  0x000062aaf6db8227 in em_hardware_init (hw=hw@entry=0x1586788c0)
>>      at ../sources/drivers/net/intel/e1000/em_ethdev.c:920
>> #6  0x000062aaf65340ff in em_hw_init (hw=0x1586788c0) at ../sources/drivers/net/intel/e1000/em_ethdev.c:445
>> #7  eth_em_dev_init (eth_dev=eth_dev@entry=0x62aaff346000 <rte_eth_devices>)
>>      at ../sources/drivers/net/intel/e1000/em_ethdev.c:314
>> #8  0x000062aaf6db8b71 in rte_eth_dev_pci_generic_probe (private_data_size=11240,
>>      dev_init=0x62aaf6db8310 <eth_em_dev_init>, pci_dev=0x62ab2853dd90) at ../sources/lib/ethdev/ethdev_pci.h:150
>> #9  eth_em_pci_probe (pci_drv=<optimized out>, pci_dev=0x62ab2853dd90)
>>      at ../sources/drivers/net/intel/e1000/em_ethdev.c:365
>> #10 0x000062aaf646adf5 in rte_pci_probe_one_driver (dr=dr@entry=0x62aaf82d8020 <rte_em_pmd>,
>>      dev=dev@entry=0x62ab2853dd90) at ../sources/drivers/bus/pci/pci_common.c:299
>> #11 0x000062aaf6a15f7d in pci_probe_all_drivers (dev=0x62ab2853dd90) at ../sources/drivers/bus/pci/pci_common.c:383
>> #12 pci_probe () at ../sources/drivers/bus/pci/pci_common.c:410
>> #13 0x000062aaf7a485f3 in rte_bus_probe () at ../sources/lib/eal/common/eal_common_bus.c:84
>> #14 0x000062aaf670585d in rte_eal_init (argc=argc@entry=146, argv=argv@entry=0x7fffca468898)
>>      at ../sources/lib/eal/linux/eal.c:1253
>>
>> The crash is linked to the use of gcc-13: uner Ubuntu-24.04 testpmd
>> compiled with gcc-11 from the same DPDK tree works as expected.
>>
>> The perfect solution would be for someone to investigate why the
>> PMD crashes. However, this depends on Maintainer availability.
>>
>> A less-perfect solution is to reduce the optimization level
>> (like another proposal for net/qede: see Link).
>>
>> Note: if more regressions are seen in less-frequently used PMDs,
>>        maybe we should switch the default optimization level to -O1,
>>        (tree-wide) and only rise the optimization level for actively
>>        maintained PMDs, which are proven to work as expected with
>>        higher optimization levels.
>>
>> Link: http://patches.dpdk.org/project/dpdk/patch/20250909054023.3263401-1-thierry.herbelot@6wind.com/
>> Signed-off-by: Thierry Herbelot <thierry.herbelot@6wind.com>
> 
> NAK.
> Please RCA this rather than hiding such an issue.

Hello David,

As said in the commit log, this is clearly a Maintainer issue, who will 
have the hardware documentation. The PMD is broken, and this was not 
seen until a new gcc is used.

We can not expect a random developer to sprinkle memory barriers in the 
PMD until testpmd seems to be working.

	Best regards

	Thierry


-- 
Thierry Herbelot