On Wed, Aug 07, 2024 at 04:51:53PM +0100, James Clark wrote:
For other PMUs, PERF_SAMPLE_PHYS_ADDR requires perf_allow_kernel()
rather than just perfmon_capable(). Because PMSCR_EL1_PA is another form
of physical address, make it consistent and use perf_allow_kernel() for
SPE as well. PMSCR_EL1_PCT and PMSCR_EL1_CX also get the same change.
This improves consistency and indirectly fixes the following error
message which is misleading because perf_event_paranoid is not taken
into account by perfmon_capable():
$ perf record -e arm_spe/pa_enable/
Error:
Access to performance monitoring and observability operations is
limited. Consider adjusting /proc/sys/kernel/perf_event_paranoid
setting ...
Suggested-by: Al Grant <al.grant@xxxxxxx>
Signed-off-by: James Clark <james.clark@xxxxxxxxxx>
---
Changes since v1:
* Export perf_allow_kernel() instead of sysctl_perf_event_paranoid
drivers/perf/arm_spe_pmu.c | 9 ++++-----
include/linux/perf_event.h | 8 +-------
kernel/events/core.c | 9 +++++++++
3 files changed, 14 insertions(+), 12 deletions(-)
diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
index 9100d82bfabc..3569050f9cf3 100644
--- a/drivers/perf/arm_spe_pmu.c
+++ b/drivers/perf/arm_spe_pmu.c
@@ -41,7 +41,7 @@
/*
* Cache if the event is allowed to trace Context information.
- * This allows us to perform the check, i.e, perfmon_capable(),
+ * This allows us to perform the check, i.e, perf_allow_kernel(),
* in the context of the event owner, once, during the event_init().
*/
#define SPE_PMU_HW_FLAGS_CX 0x00001
@@ -50,7 +50,7 @@ static_assert((PERF_EVENT_FLAG_ARCH & SPE_PMU_HW_FLAGS_CX) == SPE_PMU_HW_FLAGS_C
static void set_spe_event_has_cx(struct perf_event *event)
{
- if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && perfmon_capable())
+ if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && !perf_allow_kernel(&event->attr))
event->hw.flags |= SPE_PMU_HW_FLAGS_CX;
The rationale for this change in the commit message is because other
drivers gate PERF_SAMPLE_PHYS_ADDR on perf_allow_kernel(). However,
putting the PID in contextidr doesn't seem to have anything to do with
that...
}
@@ -745,9 +745,8 @@ static int arm_spe_pmu_event_init(struct perf_event *event)
set_spe_event_has_cx(event);
reg = arm_spe_event_to_pmscr(event);
- if (!perfmon_capable() &&
- (reg & (PMSCR_EL1_PA | PMSCR_EL1_PCT)))
- return -EACCES;
+ if (reg & (PMSCR_EL1_PA | PMSCR_EL1_PCT))
Similarly here. What does the physical counter have to do with physical
address sampling other than sharing the word "physical"?
Will