On Mon, 29 Jun 2020 10:19:10 +0100 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: > > > On Fri, 26 Jun 2020 15:59:57 +0100 > > > 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>
