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

[Thomas Monjalon <thomas@monjalon.net>]

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.
> 
> 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.
> 
> > 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?

Do you mean drivers need to be fixed?