On Thu, 28 Oct 2021 16:40:28 +0100 "Burakov, Anatoly" <anatoly.bura...@intel.com> wrote:
> On 28-Oct-21 3:53 PM, Thomas Monjalon wrote: > > 28/10/2021 13:32, Ferruh Yigit: > >> On 10/28/2021 12:11 PM, Xia, Chenbo wrote: > >>>> -----Original Message----- > >>>> From: Burakov, Anatoly <anatoly.bura...@intel.com> > >>>> Sent: Thursday, October 28, 2021 6:30 PM > >>>> To: Xia, Chenbo <chenbo....@intel.com>; dev@dpdk.org > >>>> Subject: Re: [dpdk-dev] [PATCH v1 1/2] vfio: make API return values > >>>> consistent > >>>> > >>>> Hi Chenbo, > >>>> > >>>>> And do we need backport? As 'return -1' does not align with the API > >>>>> doxygen. > >>>>> > >>>>> Thanks, > >>>>> Chenbo > >>>>> > >>>> Maybe it's the FreeBSD implementation that needs to be adjusted then, > >>>> because none of those functions are valid on FreeBSD, and the > >>>> documentation for VFIO functions explicitly mentions that on FreeBSD, > >>>> they should return an error. I went with adjusting Linux implementation > >>>> to minimize the amount of changes we have to make (and only change code > >>>> path that no one uses in the first place), but maybe that was a wrong > >>>> decision. > >>>> > >>>> I'm not sure if changing the API return value to match what was > >>>> documented counts as an API change, so maybe backport to stable is not > >>>> advised here. > >>> > >>> It's not a API change. My point is whether VFIO is present, users just use > >>> the API to check if vfio support is there. In a kernel version that does > >>> not > >>> support VFIO, he uses 'if(rte_vfio_is_enabled(XXX))' to check as the > >>> doxygen > >>> says its return value should be 1 as true or 0 as false. He will get true > >>> (-1) > >>> but VFIO is not there. That's why I think it's a bug and should be > >>> backported. > >>> > >>> But I think we can first discuss if we should drop the dummy > >>> implementation > >>> as DPDK requires Linux kernel version >= 4.4 now so VFIO is always > >>> present. > >>> I think it depends on by saying 'DPDK requires kernel version >= 4.4'. > >>> It's > >>> a real _requirement_ or only a recommendation? > >>> > >>> Ferruh, David & Thomas, What do you think? > >>> > >> > >> My understanding is, it is a requirement. DPDK does not guarantee support > >> for > >> kernels < 4.4. > > > > Do we have a kernel version check at runtime? > > I think we should add a warning if running too old kernel. > > > > Perhaps we should (there's a `uname()` call, should be fairly > straightforward to implement), but obviously this would be outside the > scope for this patchset. > Checking kernel version at runtime with uname() is a bad idea because enterprise distro vendors support things without updating the kernel version. It is always better to try for the feature and handle errors that could be reported by older kernels. Also DPDK System Requirements says kernel >= 4.4 on Linux.
