29/06/2020 18:15, Bruce Richardson: > On Mon, Jun 29, 2020 at 08:41:46AM -0700, Stephen Hemminger wrote: > > Bruce Richardson <bruce.richard...@intel.com> wrote: > > > On Mon, Jun 29, 2020 at 10:11:58AM +0100, Bruce Richardson wrote: > > > > On Fri, Jun 26, 2020 at 10:05:42AM -0700, Stephen Hemminger wrote: > > > > > Bruce Richardson <bruce.richard...@intel.com> wrote: > > > > > > > > > > > When using statically linked DPDK binaries, the EAL checks the > > > > > > default PMD > > > > > > path and tries to load any drivers there, despite the fact that all > > > > > > drivers > > > > > > are normally linked into the binary. This behaviour can cause > > > > > > issues if > > > > > > the PMD path and lib dir is configured to a non-standard location > > > > > > which is > > > > > > not in the ld.so.conf paths, e.g. a build with prefix set to a home > > > > > > directory location. In a case such as this, EAL will try and > > > > > > (unnecessarily) load the .so driver files but that load will fail > > > > > > as their > > > > > > dependent libraries, such as ethdev, for example, will not be found. > > > > > > > > > > > > Because of this, it is better if statically linked DPDK apps do not > > > > > > load > > > > > > drivers from the standard paths automatically. The user can always > > > > > > have > > > > > > this behaviour by explicitly specifying the path using -d flag, if > > > > > > so > > > > > > desired. > > > > > > > > > > > > Not loading the libraries automatically can also prevent potential > > > > > > issues > > > > > > with a user building and running a statically-linked DPDK binary > > > > > > based off > > > > > > a private copy of DPDK, while there exists on the same machine a > > > > > > system-wide installation of DPDK in the default locations. Without > > > > > > this > > > > > > change, the system-installed drivers will be loaded to the binary > > > > > > alongside > > > > > > the statically-linked drivers, which is not what the user would have > > > > > > intended. > > > > > > > > > > > > To detect whether we are in a statically or dynamically linked > > > > > > binary, we > > > > > > can have EAL try to get a dlopen handle to its own shared library, > > > > > > by > > > > > > calling dlopen with the RTLD_NOLOAD flag. This will return NULL if > > > > > > there is > > > > > > no such shared lib loaded i.e. the code is executing from a static > > > > > > library, > > > > > > or a handle to the lib if it is loaded. > > > > > > > > > > > > Signed-off-by: Bruce Richardson <bruce.richard...@intel.com> > > > > > > > > > > But what if the majority of the DPDK is statically linked but the > > > > > application wants also load a dynamically linked driver? > > > > > > > > > They use the -d flag as now. The only change here is that we don't > > > > *automatically* (and silently) attempt to load all drivers from a system > > > > location when you have a static binary. > > > > > > I'd also make a couple of additional points: > > > 1. If you have a static app and you have extra drivers in your > > > EAL_PMD_PATH > > > directory you have no way of preventing the loading of them. > > > > > > 2. Since all DPDK apps try to load all files in that directory, all one > > > has > > > to do is put a non-loadable file into the DPDK PMD directory and suddenly > > > all DPDK apps on the system will fail to run. [Patchset > > > http://patches.dpdk.org/project/dpdk/list/?series=10553 will also help > > > here] > > > > > > 3. Since this is a behaviour change, perhaps it needs to be deferred to > > > 20.11? Ideally I think we should fix this now, because I think the current > > > behaviour doesn't make sense and causes more problems than it solves, but > > > if it needs to be deferred, so be it. > > > > > > Thanks, just trying to poke the corners of this change. > > Please make sure the documentation and web site match the behavior. > > > > Acked-by: Stephen Hemminger <step...@networkplumber.org> > > This appears to be a gap, since I looked through the docs and couldn't find > any reference to this behaviour at all. However, I may well have missed > something so please flag if so.
Yes we are lacking some doc around the basics of EAL (and also ethdev). This is a behaviour change, but I prefer applying it in 20.08, so we can get some user feedback before the LTS release. Applied, thanks
