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

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 12/19/2017 12:47 PM, Andrew Rybchenko wrote:
> 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.

Done [1]

[1] http://dpdk.org/ml/archives/dev/2017-December/084526.html