[dpdk-dev] [PATCH] net/nfp: fix lock file usage

Ferruh Yigit ferruh.yigit at intel.com
Thu May 24 16:15:54 CEST 2018


On 5/24/2018 3:13 PM, Ferruh Yigit wrote:
> On 5/24/2018 3:02 PM, Alejandro Lucero wrote:
>>
>>
>> On Thu, May 24, 2018 at 11:18 AM, Ferruh Yigit <ferruh.yigit at intel.com
>> <mailto:ferruh.yigit at intel.com>> wrote:
>>
>>     On 5/23/2018 5:50 PM, Alejandro Lucero wrote:
>>     > 
>>     > 
>>     > On Wed, May 23, 2018 at 4:57 PM, Ferruh Yigit <ferruh.yigit at intel.com <mailto:ferruh.yigit at intel.com>
>>     > <mailto:ferruh.yigit at intel.com <mailto:ferruh.yigit at intel.com>>> wrote:
>>     > 
>>     >     On 5/23/2018 1:28 PM, Alejandro Lucero wrote:
>>     >     > DPDK apps can be executed as non-root users but current NFP lock
>>     >     > file for avoiding concurrent accesses to CPP interface is precluding
>>     >     > this option or requires to modify system file permissions.
>>     >     > 
>>     >     > When the NFP device is bound to VFIO, this driver does not allow this
>>     >     > concurrent access, so the lock file is not required at all.
>>     >     > 
>>     >     > OVS-DPDK as executed in RedHat distributions is the main NFP user
>>     >     > needing this fix.
>>     >     > 
>>     >     > Fixes: c7e9729da6b5 ("net/nfp: support CPP")
>>     >     > 
>>     >     > Signed-off-by: Alejandro Lucero <alejandro.lucero at netronome.com
>>     <mailto:alejandro.lucero at netronome.com>
>>     <mailto:alejandro.lucero at netronome.com <mailto:alejandro.lucero at netronome.com>>>
>>     > 
>>     >     Hi Alejandro,
>>     > 
>>     >     As far as I understand this is to fix a common use case for nfp, but it looks
>>     >     like there is already a workaround and only for non-root users.
>>     > 
>>     > 
>>     > There is a patch submitted to stable versions because this lock was also with
>>     > the old NSPU interface, but as far as I know, there is no patch yet for the
>>     > current upstream tip.
>>     > 
>>     >  
>>     > 
>>     >     What is the priority of the patch, only critical but fixes allowed at this
>>     >     point, can we push this one to next release?
>>     > 
>>     > 
>>     > This is critical for us because RedHat wants to support OVS with our card, and
>>     > when OVS-DPDK is used, this problem is precluding non-root users to execute
>>     > OVS-DPDK.
>>
>>     What exactly this lock for? Does it to prevent multiple primary process to
>>     access CPP interface?
>>
>>     If so this is the know limitation in DPDK, not two separate process can driver
>>     same hardware, this is valid for all devices, why adding a lock unique to nfp?
>>
>>
>> Time ago I had, by mistake, two different DPDK processes using same device, and
>> with UIO, there is no one avoiding this.
>>
>> You can bound a device to UIO, igb_uio, and then use two different processes
>> opening the /dev/uiox file, and it works. 
> 
> But this is not anything specific to nfp, isn't it?

Or let me ask something else, is this a fix for ovs-dpdk regular use-case with
nfp? Or this is just an extra protection in case multiple process may try to use
the NIC. If second, why it is critical?

> 
>>
>> The VFIO driver does avoid this situation, but this lock is required for UIO.
>>
> 



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