arm64: perf: Ignore exclude_hv when kernel is running in HYP

commit d98ecdaca296 ("arm64: perf: Count EL2 events if the kernel is
running in HYP") returns -EINVAL when perf system call perf_event_open is
called with exclude_hv != exclude_kernel. This change breaks applications
on VHE enabled ARMv8.1 platforms. The issue was observed with HHVM
application, which calls perf_event_open with exclude_hv = 1 and
exclude_kernel = 0.

There is no separate hypervisor privilege level when VHE is enabled, the
host kernel runs at EL2. So when VHE is enabled, we should ignore
exclude_hv from the application. This behaviour is consistent with PowerPC
where the exclude_hv is ignored when the hypervisor is not present and with
x86 where this flag is ignored.

Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@cavium.com>
[will: added comment to justify the behaviour of exclude_hv]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 16 insertions, 7 deletions

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index bcc79471b38e..83a1b1ad189f 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -877,15 +877,24 @@ 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 we're running in hyp mode, then we *are* the hypervisor.
+         * Therefore we ignore exclude_hv in this configuration, since
+         * there's no hypervisor to sample anyway. This is consistent
+         * with other architectures (x86 and Power).
+         */
+        if (is_kernel_in_hyp_mode()) {
+                if (!attr->exclude_kernel)
+                        config_base |= ARMV8_PMU_INCLUDE_EL2;
+        } else {
+                if (attr->exclude_kernel)
+                        config_base |= ARMV8_PMU_EXCLUDE_EL1;
+                if (!attr->exclude_hv)
+                        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)
-                config_base |= ARMV8_PMU_INCLUDE_EL2;
 
         /*
          * Install the filter into config_base as this is used to