On Thu, May 24, 2018 at 5:30 PM, Ferruh Yigit <ferruh.yi...@intel.com> wrote:
> On 5/24/2018 4:39 PM, Alejandro Lucero wrote: > > > > > > On Thu, May 24, 2018 at 3:15 PM, Ferruh Yigit <ferruh.yi...@intel.com > > <mailto:ferruh.yi...@intel.com>> wrote: > > > > 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.yi...@intel.com > > <mailto:ferruh.yi...@intel.com> > > >> <mailto:ferruh.yi...@intel.com <mailto:ferruh.yi...@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.yi...@intel.com <mailto:ferruh.yi...@intel.com> > > <mailto:ferruh.yi...@intel.com <mailto:ferruh.yi...@intel.com>> > > >> > <mailto:ferruh.yi...@intel.com <mailto: > ferruh.yi...@intel.com> > > <mailto:ferruh.yi...@intel.com <mailto:ferruh.yi...@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.luc...@netronome.com <mailto:alejandro.lucero@ > netronome.com> > > >> <mailto:alejandro.luc...@netronome.com > > <mailto:alejandro.luc...@netronome.com>> > > >> <mailto:alejandro.luc...@netronome.com > > <mailto:alejandro.luc...@netronome.com> > > <mailto:alejandro.luc...@netronome.com > > <mailto:alejandro.luc...@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? > > > > > > I think any device bound to UIO could end up being used by two different > DPDK > > processes. So this is a protection against that possibility, because > accessing > > the NFP through the new CPP interface could make the NFP a brick even it > could > > crash the system. > > Yes and I was suggesting if we solve this, we should solve in higher level > instead of PMD, but that is already in PMD this patch is not introducing > it. > > > > > RH is configuring OVS-DPDK for running as non-root, and the lock was > precluding > > this because it is set at /var/lock which a non-root user has not access > by > > default. This patch solves the problem, because when using the device > with VFIO, > > that lock is not necessary. And with UIO, the lock is needed and > because it is > > not possible to run DPDK apps with UIO as non-root, the lock path is > fine. > > I see, this is to enable running as non-root by relaxing locking for vfio. > OK, > let me check the patch. > > But I still believe that locking shouldn't be in driver at fist place... > > Agree. I think the UIO driver should be avoiding it, but not sure if there are other reasons for not doing it. > > > > > >> > > >> The VFIO driver does avoid this situation, but this lock is > required for UIO. > > >> > > > > > > > > >
