From: Rob Herring <robh@kernel.org>
To: Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Ian Rogers <irogers@google.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
linux-kernel@vger.kernel.org, honnappa.nagarahalli@arm.com,
Raphael Gault <raphael.gault@arm.com>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Namhyung Kim <namhyung@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3 03/10] arm64: perf: Enable pmu counter direct access for perf event on armv8
Date: Fri, 11 Sep 2020 15:51:11 -0600 [thread overview]
Message-ID: <20200911215118.2887710-4-robh@kernel.org> (raw)
In-Reply-To: <20200911215118.2887710-1-robh@kernel.org>
From: Raphael Gault <raphael.gault@arm.com>
Keep track of event opened with direct access to the hardware counters
and modify permissions while they are open.
The strategy used here is the same which x86 uses: everytime an event
is mapped, the permissions are set if required. The atomic field added
in the mm_context helps keep track of the different event opened and
de-activate the permissions when all are unmapped.
We also need to update the permissions in the context switch code so
that tasks keep the right permissions.
Signed-off-by: Raphael Gault <raphael.gault@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
---
v2:
- Move mapped/unmapped into arm64 code. Fixes arm32.
- Rebase on cap_user_time_short changes
Changes from Raphael's v4:
- Drop homogeneous check
- Disable access for chained counters
- Set pmc_width in user page
---
arch/arm64/include/asm/mmu.h | 5 ++++
arch/arm64/include/asm/mmu_context.h | 2 ++
arch/arm64/include/asm/perf_event.h | 14 ++++++++++
arch/arm64/kernel/perf_event.c | 41 ++++++++++++++++++++++++++++
4 files changed, 62 insertions(+)
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index a7a5ecaa2e83..52cfdb676f06 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -19,6 +19,11 @@
typedef struct {
atomic64_t id;
+ /*
+ * non-zero if userspace have access to hardware
+ * counters directly.
+ */
+ atomic_t pmu_direct_access;
#ifdef CONFIG_COMPAT
void *sigpage;
#endif
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index f2d7537d6f83..d24589ecb07a 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -21,6 +21,7 @@
#include <asm/proc-fns.h>
#include <asm-generic/mm_hooks.h>
#include <asm/cputype.h>
+#include <asm/perf_event.h>
#include <asm/sysreg.h>
#include <asm/tlbflush.h>
@@ -224,6 +225,7 @@ static inline void __switch_mm(struct mm_struct *next)
}
check_and_switch_context(next);
+ perf_switch_user_access(next);
}
static inline void
diff --git a/arch/arm64/include/asm/perf_event.h b/arch/arm64/include/asm/perf_event.h
index 2c2d7dbe8a02..a025d9595d51 100644
--- a/arch/arm64/include/asm/perf_event.h
+++ b/arch/arm64/include/asm/perf_event.h
@@ -8,6 +8,7 @@
#include <asm/stack_pointer.h>
#include <asm/ptrace.h>
+#include <linux/mm_types.h>
#define ARMV8_PMU_MAX_COUNTERS 32
#define ARMV8_PMU_COUNTER_MASK (ARMV8_PMU_MAX_COUNTERS - 1)
@@ -251,4 +252,17 @@ extern unsigned long perf_misc_flags(struct pt_regs *regs);
(regs)->pstate = PSR_MODE_EL1h; \
}
+static inline void perf_switch_user_access(struct mm_struct *mm)
+{
+ if (!IS_ENABLED(CONFIG_PERF_EVENTS))
+ return;
+
+ if (atomic_read(&mm->context.pmu_direct_access)) {
+ write_sysreg(ARMV8_PMU_USERENR_ER|ARMV8_PMU_USERENR_CR,
+ pmuserenr_el0);
+ } else {
+ write_sysreg(0, pmuserenr_el0);
+ }
+}
+
#endif
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 2727d126cecd..cf44591f5be1 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -836,6 +836,41 @@ static int armv8pmu_access_event_idx(struct perf_event *event)
return event->hw.idx;
}
+static void refresh_pmuserenr(void *mm)
+{
+ perf_switch_user_access(mm);
+}
+
+static void armv8pmu_event_mapped(struct perf_event *event, struct mm_struct *mm)
+{
+ if (!(event->hw.flags & ARMPMU_EL0_RD_CNTR))
+ return;
+
+ /*
+ * This function relies on not being called concurrently in two
+ * tasks in the same mm. Otherwise one task could observe
+ * pmu_direct_access > 1 and return all the way back to
+ * userspace with user access disabled while another task is still
+ * doing on_each_cpu_mask() to enable user access.
+ *
+ * For now, this can't happen because all callers hold mmap_lock
+ * for write. If this changes, we'll need a different solution.
+ */
+ lockdep_assert_held_write(&mm->mmap_lock);
+
+ if (atomic_inc_return(&mm->context.pmu_direct_access) == 1)
+ on_each_cpu(refresh_pmuserenr, mm, 1);
+}
+
+static void armv8pmu_event_unmapped(struct perf_event *event, struct mm_struct *mm)
+{
+ if (!(event->hw.flags & ARMPMU_EL0_RD_CNTR))
+ return;
+
+ if (atomic_dec_and_test(&mm->context.pmu_direct_access))
+ on_each_cpu_mask(mm_cpumask(mm), refresh_pmuserenr, NULL, 1);
+}
+
/*
* Add an event filter to a given event.
*/
@@ -1112,6 +1147,8 @@ static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name,
cpu_pmu->filter_match = armv8pmu_filter_match;
cpu_pmu->pmu.event_idx = armv8pmu_access_event_idx;
+ cpu_pmu->pmu.event_mapped = armv8pmu_event_mapped;
+ cpu_pmu->pmu.event_unmapped = armv8pmu_event_unmapped;
cpu_pmu->name = name;
cpu_pmu->map_event = map_event;
@@ -1272,6 +1309,10 @@ void arch_perf_update_userpage(struct perf_event *event,
userpg->cap_user_time = 0;
userpg->cap_user_time_zero = 0;
userpg->cap_user_time_short = 0;
+ userpg->cap_user_rdpmc = !!(event->hw.flags & ARMPMU_EL0_RD_CNTR);
+
+ if (userpg->cap_user_rdpmc)
+ userpg->pmc_width = armv8pmu_event_is_64bit(event) ? 64 : 32;
do {
rd = sched_clock_read_begin(&seq);
--
2.25.1
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next prev parent reply other threads:[~2020-09-11 21:53 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-11 21:51 [PATCH v3 0/10] libperf and arm64 userspace counter access support Rob Herring
2020-09-11 21:51 ` [PATCH v3 01/10] arm64: pmu: Add hook to handle pmu-related undefined instructions Rob Herring
2020-09-28 18:26 ` Will Deacon
2020-09-29 13:46 ` Rob Herring
2020-09-29 17:49 ` Will Deacon
2020-09-29 20:46 ` Rob Herring
2020-09-11 21:51 ` [PATCH v3 02/10] arm64: pmu: Add function implementation to update event index in userpage Rob Herring
2020-09-11 21:51 ` Rob Herring [this message]
2020-09-11 21:51 ` [PATCH v3 04/10] tools/include: Add an initial math64.h Rob Herring
2020-09-11 21:51 ` [PATCH v3 05/10] libperf: Add libperf_evsel__mmap() Rob Herring
2020-09-18 14:33 ` Jiri Olsa
2020-09-22 15:28 ` Rob Herring
2020-09-22 18:32 ` Jiri Olsa
2020-09-11 21:51 ` [PATCH v3 06/10] libperf: tests: Add support for verbose printing Rob Herring
2020-09-11 21:51 ` [PATCH v3 07/10] libperf: Add support for user space counter access Rob Herring
2020-09-11 21:51 ` [PATCH v3 08/10] libperf: Add arm64 support to perf_mmap__read_self() Rob Herring
2020-09-11 21:51 ` [PATCH v3 09/10] perf: arm64: Add test for userspace counter access on heterogeneous systems Rob Herring
2020-09-11 21:51 ` [PATCH v3 10/10] Documentation: arm64: Document PMU counters access from userspace Rob Herring
2020-09-12 20:53 ` [PATCH v3 0/10] libperf and arm64 userspace counter access support Jiri Olsa
2020-09-14 14:21 ` Rob Herring
[not found] ` <CANW9uytmafiNb_8oua9QY7L9O5BQTBFQBOMS3ZgjQ7aWj8CD2Q@mail.gmail.com>
2020-09-16 2:50 ` Rob Herring
2020-09-19 7:22 ` Itaru Kitayama
2020-09-22 15:23 ` Rob Herring
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