On Tue, Apr 04, 2017 at 05:37:10PM +0530, Ganapatrao Kulkarni wrote: > On Tue, Apr 4, 2017 at 4:48 PM, Will Deacon <will.dea...@arm.com> wrote: > > On Tue, Apr 04, 2017 at 04:10:55PM +0530, Ganapatrao Kulkarni wrote: > >> commit d98ecda (arm64: perf: Count EL2 events if the kernel is running in > >> HYP) > >> is returning error for perf syscall with mixed attribute set for > >> exclude_kernel > >> and exlude_hv. > >> > >> This change is breaking some applications (observed with hhvm) when > >> ran with VHE enabled. Adding change to enable EL2 event counting, > >> if either of or both of exclude_kernel and exlude_hv are not set. > >> > >> Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulka...@cavium.com> > >> --- > >> arch/arm64/kernel/perf_event.c | 19 ++++++++++++------- > >> 1 file changed, 12 insertions(+), 7 deletions(-) > > > > Hmm. When we have VHE, we can't distinguish between hypervisor and kernel, > > so this patch doesn't seem right to me. The code currently requires > > both exclude_kernel and exclude_hv to be clear before we enable profiling > > EL2, otherwise we're failing to exclude samples that were asked to be > > excluded. > > The application cant differentiate that kernel is running in EL2/VHE or in EL1 > when VHE=1, is it makes sense to enable EL2 event counting when there > is request from application to either include kernel or hypervisor > event count, since both are same.
You can make exactly the same argument against your proposal by saying that it makes sense to disable EL2 event counting when there is a request from an application to either exclude kernel or hypervisor event counting. > IMO, it is not appropriate to have different application behaviour > when kernel booted with VHE=0/1 Then find another solution to that. How about a mechanism to advertise that exclude_hv is effectively always set if the kernel is running at EL2? That would mean that you would use exclude_kernel to determine the profiling controls for the host. Will