Re: [dpdk-dev] [PATCH v2] Fixes: ethdev: secondary process change shared memory

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 1/16/2020 7:43 AM, Andrew Rybchenko wrote:
> On 1/15/20 11:43 PM, Thomas Monjalon wrote:
>> 15/01/2020 19:35, Ferruh Yigit:
>>> On 1/15/2020 6:49 AM, 方统浩50450 wrote:
>>>> Hi Ferruh, thanks for your message.
>>>>
>>>>
>>>> We developed a ethtool-dpdk which is secondary process based dpdk 17.08 version. Our device
>>>> support hotplug detach, but hotplug deatch is failed when we use ethtool-dpdk.We found the
>>>> secondary process will change the shared memory when initializing.Secondary process calls
>>>> "rte_eth_dev_pci_allocate" function and enters "rte_eth_copy_pci_info" function.
>>>> (rte_eth_dev_pci_generic_probe -> rte_eth_dev_pci_allocate -> rte_eth_copy_pci_info)
>>>> Then it sets the value of struct "rte_eth_dev_data.dev_flags" to zero.In our platform, this value
>>>> is equal to 0x0003.(RTE_ETH_DEV_DETACHABLE | RTE_ETH_DEV_INTR_LSC),but after reset
>>>> the "dev_flags", the value changed to 0x0002.(RTE_ETH_DEV_DETACHABLE).So, our device hotplug
>>>> detach is failed.I found the similar problem in other dpdk version, include dpdk 19.11.Even though
>>>> the deivce hotplug detach is discarded,but i think the shared memory changed is unexpected by primary
>>>> process.
> 
> Hold on, just for my understanding. As far as I can see
> RTE_ETH_DEV_DETACHABLE was removed in 17.11. Does it
> change something in above description?

Overall secondary overwrites primary values, I think we should fix it
independent from the flags involved.

> 
>>> I agree this is the problem.
>>> In the driver code, 'rte_eth_copy_pci_info' is called only by primary process,
>>>
>>> but the generic code is faulty.
>>>
>>> And in 19.11 additionally 'eth_dev_pci_specific_init' also seems has same problem.
> 
> Yes, as I understand RTE_ETH_DEV_CLOSE_REMOVE,
> RTE_ETH_DEV_BONDED_SLAVE, RTE_ETH_DEV_REPRESENTOR and
> RTE_ETH_DEV_NOLIVE_MAC_ADDR may be lost because of
> reinit (if not restored in other branches). Bad anyway.
> 
>>>> Our driver is ixgbe, i think this problem has a little relationship with driver, Secondary process
>>>> enters "rte_eth_copy_pci_info" by "rte_eth_dev_pci_allocate".And I agree your opinion, the helper
>>>> function should simple on what it does.I have two ways to fix this problem, one is add an if-statement
>>>>
>>>> in "rte_eth_dev_pci_allocate" function to forbid secondary process enters "rte_eth_copy_pci_info" function,
>>>> another way is add an if-statement in "rte_eth_copy_pci_info" function to forbid secondary process change
>>>> shared memory.And First way need to ensure the "rte_eth_copy_pci_info" function won't be called anywhere else.
>>>> I think the second way is simple and lower risk.
>>>
>>> Yes these are the two options.
>>>
>>> I agree adding check in the 'rte_eth_copy_pci_info' covers all cases and safer.
>>> BUT my concern was adding decision making to simple/leaf function and make it
>>> harder to debug/use, instead of giving what primary/secondary process should
>>> call decision in higher level.
>>>
>>> But I just recognized that some PMDs are calling 'rte_eth_copy_pci_info' on
>>> secondary process, like mlx4 or szedata2, and most probably this is not their
>>> intention.
>>> And 'eth_dev->intr_handle' set in 'rte_eth_copy_pci_info', not calling this
>>> function may have side affect of 'eth_dev->intr_handle' not set in secondary.
>>>
>>> With above considerations I am OK to your proposal to cover all cases, Thomas,
>>> Andrew, any concern?
> 
> I would put if condition in rte_eth_copy_pci_info().
> It is the function which writes shared space from
> secondary process when it should not be done and it
> should be fixed there.

OK

> 
>> Do you mean drivers need to be fixed?
> 
> I'm not sure that I fully understand it. Since copy function
> cares about intr_handle copying I'm afraid that it is not
> 100% correct to skip it in secondary process completely as
> many drivers do right now. Basically it makes eth_dev structure
> in secondary process inconsistent. However, it looks like
> most of these drivers simply obtain handle from pci_dev
> directly and it explains why they are not affected.
> There are exceptions which are potentially bugs, e.g.
> drivers/net/ice/ice_ethdev.c: ice_interrupt_handler at the end.
> 
> I think that it would be better if intr_handle is always
> correct in eth_dev (both primary and secondary cases) and
> drivers use it instead of the same from pci_dev.
> 

OK

So this suggest going on with Fang's patch. I only requested an additional note
in function comment related to this secondary check.