It's a good fix, you can drop the RFC in commit title. :) The title could be more specific, like:
fpga: dfl: fme: Fix cpu hotplug issue in performance reporting So we know it is for performance reporting feature at first glance. On Mon, Jun 28, 2021 at 12:45:46PM +0530, Kajol Jain wrote: > Commit 724142f8c42a ("fpga: dfl: fme: add performance > reporting support") added performance reporting support > for FPGA management engine via perf. May drop this section, it is indicated in the Fixes tag. > > It also added cpu hotplug feature but it didn't add The performance reporting driver added cpu hotplug ... > pmu migration call in cpu offline function. > This can create an issue incase the current designated > cpu being used to collect fme pmu data got offline, > as based on current code we are not migrating fme pmu to > new target cpu. Because of that perf will still try to > fetch data from that offline cpu and hence we will not > get counter data. > > Patch fixed this issue by adding pmu_migrate_context call > in fme_perf_offline_cpu function. > > Fixes: 724142f8c42a ("fpga: dfl: fme: add performance reporting support") > Signed-off-by: Kajol Jain <kj...@linux.ibm.com> Tested-by: Xu Yilun <yilun...@intel.com> Thanks, Yilun > --- > drivers/fpga/dfl-fme-perf.c | 4 ++++ > 1 file changed, 4 insertions(+) > > --- > - This fix patch is not tested (as I don't have required environment). > But issue mentioned in the commit msg can be re-created, by starting any > fme_perf event and while its still running, offline current designated > cpu pointed by cpumask file. Since current code didn't migrating pmu, > perf gonna try getting counts from that offlined cpu and hence we will > not get event data. > --- > diff --git a/drivers/fpga/dfl-fme-perf.c b/drivers/fpga/dfl-fme-perf.c > index 4299145ef347..b9a54583e505 100644 > --- a/drivers/fpga/dfl-fme-perf.c > +++ b/drivers/fpga/dfl-fme-perf.c > @@ -953,6 +953,10 @@ static int fme_perf_offline_cpu(unsigned int cpu, struct > hlist_node *node) > return 0; > > priv->cpu = target; > + > + /* Migrate fme_perf pmu events to the new target cpu */ > + perf_pmu_migrate_context(&priv->pmu, cpu, target); > + > return 0; > } > > -- > 2.31.1