On 15/02/16 17:22, Will Deacon wrote:

On Thu, Feb 11, 2016 at 06:40:01PM +0000, Marc Zyngier wrote:

quoted

When the kernel is running in HYP (with VHE), it is necessary to
include EL2 events if the user requests counting kernel or
hypervisor events.

Reviewed-by: Christoffer Dall <redacted>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <redacted>
---
 arch/arm64/kernel/perf_event.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index f7ab14c..6013a38 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c

@@ -20,6 +20,7 @@
  */
 
 #include <asm/irq_regs.h>
+#include <asm/virt.h>
 
 #include <linux/of.h>
 #include <linux/perf/arm_pmu.h>

@@ -693,10 +694,15 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event,
 		return -EPERM;
 	if (attr->exclude_user)
 		config_base |= ARMV8_EXCLUDE_EL0;
-	if (attr->exclude_kernel)
-		config_base |= ARMV8_EXCLUDE_EL1;
-	if (!attr->exclude_hv)
-		config_base |= ARMV8_INCLUDE_EL2;
+	if (is_kernel_in_hyp_mode()) {
+		if (!attr->exclude_kernel || !attr->exclude_hv)
+			config_base |= ARMV8_INCLUDE_EL2;

Hmm, so if userspace sets exclude_kernel but not exclude_user and
exclude_hv, what should we do? I'm slightly tempted to reject the
filter with -EINVAL...

I was angling for the minimum level of surprise for the user, but
I guess that the results are going to be troubling anyway.

How about something like this on top:

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 6013a38..8c00ed4 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c

@@ -695,7 +695,10 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event,
 	if (attr->exclude_user)
 		config_base |= ARMV8_EXCLUDE_EL0;
 	if (is_kernel_in_hyp_mode()) {
-		if (!attr->exclude_kernel || !attr->exclude_hv)
+		/* Demand that kernel and hv are consistent */
+		if (attr->exclude_kernel != attr->exclude_hv)
+			return -EINVAL;
+		if (!attr->exclude_hv)
 			config_base |= ARMV8_INCLUDE_EL2;
 	} else {
 		if (attr->exclude_kernel)

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...