Re: [dpdk-dev] [RFC 2/2] nfp: allow for non-root user

[Aaron Conole <aconole@redhat.com>]

Alejandro Lucero <alejandro.lucero@netronome.com> writes:

> On Tue, Apr 17, 2018 at 8:19 PM, Aaron Conole <aconole@redhat.com> wrote:
>
>  Alejandro Lucero <alejandro.lucero@netronome.com> writes:
>
>  > I was just wondering, if device device PCI sysfs resource files or VFIO group /dev files
>  require to change
>  > permissions for non-root users, does it not make sense to adjust also /var/lock in the
>  system?
>
>  For the /dev, we use udev rules - so the correct individual vfio device
>  files get assigned the correct permissions.  No such mechanism exists
>  for /var/lock as far as I can tell.
>
>  Ex. see:
>
>  https://github.com/openvswitch/ovs/blob/master/rhel/usr_lib_udev_rules.d_91-vfio.rules
>  
>
>  Maybe something similar exists that we could use to generate the lock
>  file automatically?
>
> What about /sysfs/bus/pci/device/$PCI_DEV/resource file?
>
> Is RH forcing OVS DPDK to only work if the host has IOMMU support?

Yes.

>  > On Tue, Apr 17, 2018 at 4:44 PM, Alejandro Lucero
>  <alejandro.lucero@netronome.com> wrote:
>  >
>  >  I have seen that VFIO also requires explicitly to set the right permissions for non-root
>  users to VFIO
>  >  groups under /dev/vfio. 
>  >
>  >  I assume then that running OVS or other DPDK apps as non-root is possible,
>  although requiring
>  >  those explicit permissions changes, and therefore this patch is necessary.
>  >
>  >  Adding stable@ and Thomas for discussing how can this be added to stable DPDK
>  versions even if
>  >  this is not going to be a patch for current DPDK version.
>  >
>  >  Acked-by: Alejandro Lucero <alejandro.lucero@netronome.com>
>  >
>  >  On Fri, Apr 13, 2018 at 4:31 PM, Alejandro Lucero
>  <alejandro.lucero@netronome.com> wrote:
>  >
>  >  On Fri, Apr 13, 2018 at 2:31 PM, Aaron Conole <aconole@redhat.com> wrote:
>  >
>  >  Alejandro Lucero <alejandro.lucero@netronome.com> writes:
>  >
>  >  > Again, this patch is correct, but because NFP PMD needs to access
>  >  > /sys/bus/pci/devices/$DEVICE_PCI_STRING/resource$RESOURCE_ID, and these files
>  have
>  >  just
>  >  > read/write accesses for root, I do not know if this is really necessary.
>  >  >
>  >  > Being honest, I have not used a DPDK app with NFP PMD and not being root. Does
>  it
>  >  work
>  >  > with non-root users and other PMDs with same requirements regarding sysfs
>  resource
>  >  files?
>  >
>  >  We do run as non-root user definitely with Intel PMDs.
>  >
>  >  I'm not very sure about other vendors, but I think mlx pmd runs as
>  >  non-root user (and it was modified to move off of sysfs for that
>  >  reason[1]).
>  >
>  >  It is possible to not rely on sysfs resource files if device is attached to VFIO, but I
>  think that is a
>  >  must with UIO.
>  >
>  >   
>  >  I'll continue to push for more information from the testing side to find
>  >  out though.
>  >
>  >  [1]: http://dpdk.org/ml/archives/dev/2018-February/090586.html
>  >
>  >  > On Fri, Apr 13, 2018 at 12:22 AM, Aaron Conole <aconole@redhat.com> wrote:
>  >  >
>  >  >  Currently, the nfp lock files are taken from the global lock file
>  >  >  location, which will work when the user is running as root.  However,
>  >  >  some distributions and applications (notably ovs 2.8+ on RHEL/Fedora)
>  >  >  run as a non-root user.
>  >  >
>  >  >  Signed-off-by: Aaron Conole <aconole@redhat.com>
>  >  >  ---
>  >  >   drivers/net/nfp/nfp_nfpu.c | 23 ++++++++++++++++++-----
>  >  >   1 file changed, 18 insertions(+), 5 deletions(-)
>  >  >
>  >  >  diff --git a/drivers/net/nfp/nfp_nfpu.c b/drivers/net/nfp/nfp_nfpu.c
>  >  >  index 2ed985ff4..ae2e07220 100644
>  >  >  --- a/drivers/net/nfp/nfp_nfpu.c
>  >  >  +++ b/drivers/net/nfp/nfp_nfpu.c
>  >  >  @@ -18,6 +18,22 @@
>  >  >   #define NFP_CFG_EXP_BAR         7
>  >  >
>  >  >   #define NFP_CFG_EXP_BAR_CFG_BASE       0x30000
>  >  >  +#define NFP_LOCKFILE_PATH_FMT "%s/nfp%d"
>  >  >  +
>  >  >  +/* get nfp lock file path (/var/lock if root, $HOME otherwise) */
>  >  >  +static void
>  >  >  +nspu_get_lockfile_path(char *buffer, int bufsz, nfpu_desc_t *desc)
>  >  >  +{
>  >  >  +       const char *dir = "/var/lock";
>  >  >  +       const char *home_dir = getenv("HOME");
>  >  >  +
>  >  >  +       if (getuid() != 0 && home_dir != NULL)
>  >  >  +               dir = home_dir;
>  >  >  +
>  >  >  +       /* use current prefix as file path */
>  >  >  +       snprintf(buffer, bufsz, NFP_LOCKFILE_PATH_FMT, dir,
>  >  >  +                       desc->nfp);
>  >  >  +}
>  >  >
>  >  >   /* There could be other NFP userspace tools using the NSP interface.
>  >  >    * Make sure there is no other process using it and locking the access for
>  >  >  @@ -30,9 +46,7 @@ nspv_aquire_process_lock(nfpu_desc_t *desc)
>  >  >          struct flock lock;
>  >  >          char lockname[30];
>  >  >
>  >  >  -       memset(&lock, 0, sizeof(lock));
>  >  >  -
>  >  >  -       snprintf(lockname, sizeof(lockname), "/var/lock/nfp%d", desc->nfp);
>  >  >  +       nspu_get_lockfile_path(lockname, sizeof(lockname), desc);
>  >  >
>  >  >          /* Using S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH */
>  >  >          desc->lock = open(lockname, O_RDWR | O_CREAT, 0666);
>  >  >  @@ -106,7 +120,6 @@ nfpu_close(nfpu_desc_t *desc)
>  >  >          rte_free(desc->nspu);
>  >  >          close(desc->lock);
>  >  >
>  >  >  -       snprintf(lockname, sizeof(lockname), "/var/lock/nfp%d", desc->nfp);
>  >  >  -       unlink(lockname);
>  >  >  +       nspu_get_lockfile_path(lockname, sizeof(lockname), desc);
>  >  >          return 0;
>  >  >   }
>  >  >  -- 
>  >  >  2.14.3