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

[方统浩50450 <fangtonghao@sangfor.com.cn>]

>@Fang, only can you please make a new version to update the
>'rte_eth_copy_pci_info' function comment to document shared data is not updated
>for the secondary process?
>So this suggest going on with Fang's patch. I only requested an additional note
>in function comment related to this secondary check.
@Ferruh Yigit
Should I update a new version patch of "rte_eth_copy_pci_info" function and explain
wthether the regular functioning of secondary process is affected or not?
I cant figure out what you need me to do.




发件人：Ferruh Yigit <ferruh.yigit@intel.com>
发送日期：2020-01-16 17:04:09
收件人：Andrew Rybchenko <arybchenko@solarflare.com>,Thomas Monjalon <thomas@monjalon.net>
抄送人："方统浩50450" <fangtonghao@sangfor.com.cn>,dev@dpdk.org,stable@dpdk.org,jia.guo@intel.com,cunming.liang@intel.com,qi.z.zhang@intel.com,jungle845943968@outlook.com,Jerin Jacob Kollanukkaran <jerinj@marvell.com>
主题：Re: [dpdk-dev] [PATCH v2] Fixes: ethdev: secondary process change shared memory>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.