Anshuman Khandual [off-list ref] wrote:

On 06/06/2013 10:26 AM, Michael Neuling wrote:

quoted

Anshuman Khandual [off-list ref] wrote:
=20

quoted

Completely ignore BHRB privilege state filter request as we are
already configuring that with privilege state filtering attribute
for the accompanying PMU event. This would help achieve cleaner
user space interaction for BHRB.

This patch fixes a situation like this

Before patch:-
------------
./perf record -j any -e branch-misses:k ls
Error:
The sys_perf_event_open() syscall returned with 95 (Operation not supp=

orted) for event (branch-misses:k).

quoted

quoted

/bin/dmesg may provide additional information.
No CONFIG_PERF_EVENTS=3Dy kernel support configured?

Here 'perf record' actually copies over ':k' filter request into BHRB
privilege state filter config and our previous check in kernel would
fail that.

After patch:-
-------------
./perf record -j any -e branch-misses:k ls
perf  perf.data  perf.data.old  test-mmap-ring
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.002 MB perf.data (~102 samples) ]

Signed-off-by: Anshuman Khandual <redacted>
---
 arch/powerpc/perf/power8-pmu.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8=

-pmu.c

quoted

quoted

index f7d1c4f..3a58416 100644

--- a/arch/powerpc/perf/power8-pmu.c
+++ b/arch/powerpc/perf/power8-pmu.c

@@ -525,16 +525,12 @@ static u64 power8_bhrb_filter_map(u64 branch_sam=

ple_type)

quoted

quoted

 	u64 pmu_bhrb_filter =3D 0;
 	u64 br_privilege =3D branch_sample_type & ONLY_PLM;
=20=20
-	/* BHRB and regular PMU events share the same prvillege state
+	/* BHRB and regular PMU events share the same privilege state
 	 * filter configuration. BHRB is always recorded along with a
-	 * regular PMU event. So privilege state filter criteria for BHRB
-	 * and the companion PMU events has to be the same. As a default
-	 * "perf record" tool sets all privillege bits ON when no filter
-	 * criteria is provided in the command line. So as along as all
-	 * privillege bits are ON or they are OFF, we are good to go.
+	 * regular PMU event. As the privilege state filter is handled
+	 * in the basic PMC configuration of the accompanying regular
+	 * PMU event, we ignore any separate BHRB specific request.
 	 */
-	if ((br_privilege !=3D 7) && (br_privilege !=3D 0))
-		return -1;

=20
br_privilege is now unused which causes this compile error.
=20
arch/powerpc/perf/power8-pmu.c:526:6: error: unused variable =E2=80=98b=

r_privilege=E2=80=99 [-Werror=3Dunused-variable]

quoted

=20
I assume since you didn't compile test this code, you also didn't
runtime test it either?!!?!?!?

=20
=20
Always compile with the cross compiler "ARCH=3Dpowerpc
CROSS_COMPILE=3Dpowerpc64-linux-gnu- make" I copied over
arch/powerpc/config/pseries_defconfig and compiled it. Some how it
missed to be a 64 bit kernel config which resulted in shutting down
compilation of arch/powerpc/perf/power8-pmu.c file. So never
encountered this compiler warning message before. Will fix this.

I don't understand this at all... pseries_defconfig is a 64bit kernel.

BTW. you don't need to copy it.  Just do "make pseries_defconfig && make
vmlinux".

Mikey