On Thu, Apr 20, 2017 at 2:19 PM, Mark Rutland [off-list ref] wrote:

On Wed, Apr 19, 2017 at 11:14:06PM +0530, Ganapatrao Kulkarni wrote:

quoted

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 exclude_hv. This change is breaking some applications (observed with hhvm)
when ran on VHE enabled platforms.

Adding fix to consider only exclude_kernel attribute when kernel is
running in HYP. Also adding sysfs file to notify the bhehaviour
of attribute exclude_hv.

Signed-off-by: Ganapatrao Kulkarni <redacted>
---

Changelog:

V2:
 - Changes as per Will Deacon's suggestion.

V1: Initial patch

 arch/arm64/kernel/perf_event.c | 28 ++++++++++++++++++++++++----
 include/linux/perf/arm_pmu.h   |  1 +
 2 files changed, 25 insertions(+), 4 deletions(-)

@@ -871,14 +890,13 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event,

      if (attr->exclude_idle)
              return -EPERM;
-     if (is_kernel_in_hyp_mode() &&
-         attr->exclude_kernel != attr->exclude_hv)
-             return -EINVAL;
+     if (is_kernel_in_hyp_mode() && !attr->exclude_kernel)
+             config_base |= ARMV8_PMU_INCLUDE_EL2;
      if (attr->exclude_user)
              config_base |= ARMV8_PMU_EXCLUDE_EL0;
      if (!is_kernel_in_hyp_mode() && attr->exclude_kernel)
              config_base |= ARMV8_PMU_EXCLUDE_EL1;
-     if (!attr->exclude_hv)
+     if (!is_kernel_in_hyp_mode() && !attr->exclude_hv)
              config_base |= ARMV8_PMU_INCLUDE_EL2;

This isn't quite what Will suggested.

The idea was that userspace would read sysfs, then use that to determine
the correct exclusion parameters [1,2]. This logic was not expected to
change; it correctly validates whether we can provide what the user
requests.

OK, if you are ok with sysfs part, i can send next version with that
change only?.

Thanks,
Mark.

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-April/499224.html
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-April/499493.html

quoted

      /*

@@ -1008,6 +1026,8 @@ static int armv8_pmuv3_init(struct arm_pmu *cpu_pmu)
              &armv8_pmuv3_events_attr_group;
      cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_FORMATS] =
              &armv8_pmuv3_format_attr_group;
+     cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_ATTR] =
+             &armv8_pmuv3_attr_group;
      return armv8pmu_probe_pmu(cpu_pmu);
 }

diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index 8462da2..a26ffc7 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h

@@ -81,6 +81,7 @@ enum armpmu_attr_groups {
      ARMPMU_ATTR_GROUP_COMMON,
      ARMPMU_ATTR_GROUP_EVENTS,
      ARMPMU_ATTR_GROUP_FORMATS,
+     ARMPMU_ATTR_GROUP_ATTR,
      ARMPMU_NR_ATTR_GROUPS
 };

--

1.8.1.4