Re: [dpdk-dev] [PATCH] ethdev: fix setting of MAC address

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 12/19/2017 12:29 PM, Olivier MATZ wrote:
> Hi,
>
> On Mon, Dec 18, 2017 at 02:38:55PM +0300, Andrew Rybchenko wrote:
>> On 12/18/2017 01:53 PM, Igor Ryzhov wrote:
>>> On Mon, Dec 18, 2017 at 1:35 PM, Andrew Rybchenko
>>> <arybchenko@solarflare.com <mailto:arybchenko@solarflare.com>> wrote:
>>>
>>>      On 12/14/2017 08:15 PM, Olivier Matz wrote:
>>>
>>>          From: Laurent Hardy <laurent.hardy@6wind.com
>>>          <mailto:laurent.hardy@6wind.com>>
>>>
>>>          When a new mac address is set, it is saved in dev->data->mac_addrs
>>>          before the ethdev handler is called.
>>>
>>>          First, it is inconsistent with the other ethdev functions
>>>          rte_eth_dev_mac_addr_remove() and rte_eth_dev_mac_addr_add().
>>>
>>>          Moreover, it prevents the drivers from wrongly comparing the
>>>          old address
>>>          and the new one, like it's done in i40evf driver:
>>>
>>>                  if (is_same_ether_addr(mac_addr, dev->data->mac_addrs))
>>>                          return;
>>>
>>>          Fixes: 943c2d899a0c ("net/i40e: set VF MAC from VF")
>>>          Fixes: 854d8ad4ef68 ("ethdev: add default mac address modifier")
>>>          Cc: stable@dpdk.org <mailto:stable@dpdk.org>
>>>
>>>          Signed-off-by: Laurent Hardy <laurent.hardy@6wind.com
>>>          <mailto:laurent.hardy@6wind.com>>
>>>          ---
>>>            lib/librte_ether/rte_ethdev.c | 4 ++--
>>>            1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>>          diff --git a/lib/librte_ether/rte_ethdev.c
>>>          b/lib/librte_ether/rte_ethdev.c
>>>          index 4f492e3db..297c02a54 100644
>>>          --- a/lib/librte_ether/rte_ethdev.c
>>>          +++ b/lib/librte_ether/rte_ethdev.c
>>>          @@ -2643,11 +2643,11 @@
>>>          rte_eth_dev_default_mac_addr_set(uint16_t port_id, struct
>>>          ether_addr *addr)
>>>                  dev = &rte_eth_devices[port_id];
>>>                  RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->mac_addr_set,
>>>          -ENOTSUP);
>>>            +     (*dev->dev_ops->mac_addr_set)(dev, addr);
>>>          +
>>>                  /* Update default address in NIC data structure */
>>>                  ether_addr_copy(addr, &dev->data->mac_addrs[0]);
>>>            -     (*dev->dev_ops->mac_addr_set)(dev, addr);
>>>          -
>>>                  return 0;
>>>            }
>>>
>>>
>>>      NACK, unfortunately it will break net/sfc in one of branches when
>>>      a new MAC
>>>      is set using restart. It relies on the fact that a new MAC is
>>>      already available in
>>>      device data.
>>>
>>>
>>> Hello Andrew,
>>>
>>> Don't you think that it's not correct that net/sfc works that way?
>>>
>>> If we go further, dev->dev_ops->mac_addr_set not only should be called
>> before ether_addr_copy.
>>> It should  return status code, and in case of error ether_addr_copy
>>> shouldn't be
>> called at all.
>>> Am I wrong?
> Yes, I also have the same feeling.
>
>> Current behaviour is convenient. Alternative will require copy of MAC
>> address
>> to set in device private data and one more copy in the function to rollback
>> in
>> the case of failure. If there are good reasons to change behaviour, I don't
>> mind but PMDs should be reviewed carefully and fixed before the change.
> Right. The first version of the patch was just a fix of the i40e code,
> which was of course less risky. But we finally decided to to that way
> for consistency.
>
> I will review the other PMDs and send a v2 that should not break
> them. If you have any guidelines for net/sfc, they will be welcome :)

We'll send net/sfc patch today/tomorrow to fix it.

Thanks,
Andrew.