From: Athira Rajeev atrajeev@linux.vnet.ibm.com
commit aa8e21c053d72b6639ea5a7f1d3a1d0209534c94 upstream.
Perf event attritube supports exclude_kernel flag to avoid sampling/profiling in supervisor state (kernel). Based on this event attr flag, Monitor Mode Control Register bit is set to freeze on supervisor state. But sometimes (due to hardware limitation), Sampled Instruction Address Register (SIAR) locks on to kernel address even when freeze on supervisor is set. Patch here adds a check to drop those samples.
Cc: stable@vger.kernel.org Signed-off-by: Athira Rajeev atrajeev@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/1606289215-1433-1-git-send-email-atrajeev@linux.vn... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/perf/core-book3s.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -2068,6 +2068,16 @@ static void record_and_restart(struct pe perf_event_update_userpage(event);
/* + * Due to hardware limitation, sometimes SIAR could sample a kernel + * address even when freeze on supervisor state (kernel) is set in + * MMCR2. Check attr.exclude_kernel and address to drop the sample in + * these cases. + */ + if (event->attr.exclude_kernel && record) + if (is_kernel_addr(mfspr(SPRN_SIAR))) + record = 0; + + /* * Finally record data if requested. */ if (record) {