[PATCH 5.0 25/25] perf/x86/intel: Implement support for TSX Force Abort

Greg Kroah-Hartman
2019-03-12T18:11:31Z

From: "Peter Zijlstra (Intel)" <peterz@infradead.org>

Skylake (and later) will receive a microcode update to address a TSX
errata. This microcode will, on execution of a TSX instruction
(speculative or not) use (clobber) PMC3. This update will also provide
a new MSR to change this behaviour along with a CPUID bit to enumerate
the presence of this new MSR.

When the MSR gets set; the microcode will no longer use PMC3 but will
Force Abort every TSX transaction (upon executing COMMIT).

When TSX Force Abort (TFA) is allowed (default); the MSR gets set when
PMC3 gets scheduled and cleared when, after scheduling, PMC3 is
unused.

When TFA is not allowed; clear PMC3 from all constraints such that it
will not get used.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/events/intel/core.c | 74 +++++++++++++++++++++++++++++++++++++++++--
arch/x86/events/perf_event.h | 6 +++
2 files changed, 77 insertions(+), 3 deletions(-)

--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -1999,6 +1999,39 @@ static void intel_pmu_nhm_enable_all(int
intel_pmu_enable_all(added);
}

+static void intel_set_tfa(struct cpu_hw_events *cpuc, bool on)
+{
+ u64 val = on ? MSR_TFA_RTM_FORCE_ABORT : 0;
+
+ if (cpuc->tfa_shadow != val) {
+ cpuc->tfa_shadow = val;
+ wrmsrl(MSR_TSX_FORCE_ABORT, val);
+ }
+}
+
+static void intel_tfa_commit_scheduling(struct cpu_hw_events *cpuc, int idx, int cntr)
+{
+ /*
+ * We're going to use PMC3, make sure TFA is set before we touch it.
+ */
+ if (cntr == 3 && !cpuc->is_fake)
+ intel_set_tfa(cpuc, true);
+}
+
+static void intel_tfa_pmu_enable_all(int added)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+
+ /*
+ * If we find PMC3 is no longer used when we enable the PMU, we can
+ * clear TFA.
+ */
+ if (!test_bit(3, cpuc->active_mask))
+ intel_set_tfa(cpuc, false);
+
+ intel_pmu_enable_all(added);
+}
+
static void enable_counter_freeze(void)
{
update_debugctlmsr(get_debugctlmsr() |
@@ -3354,6 +3387,26 @@ glp_get_event_constraints(struct cpu_hw_
return c;
}

+static bool allow_tsx_force_abort = true;
+
+static struct event_constraint *
+tfa_get_event_constraints(struct cpu_hw_events *cpuc, int idx,
+ struct perf_event *event)
+{
+ struct event_constraint *c = hsw_get_event_constraints(cpuc, idx, event);
+
+ /*
+ * Without TFA we must not use PMC3.
+ */
+ if (!allow_tsx_force_abort && test_bit(3, c->idxmsk)) {
+ c = dyn_constraint(cpuc, c, idx);
+ c->idxmsk64 &= ~(1ULL << 3);
+ c->weight--;
+ }
+
+ return c;
+}
+
/*
* Broadwell:
*
@@ -3448,13 +3501,15 @@ int intel_cpuc_prepare(struct cpu_hw_eve
goto err;
}

- if (x86_pmu.flags & PMU_FL_EXCL_CNTRS) {
+ if (x86_pmu.flags & (PMU_FL_EXCL_CNTRS | PMU_FL_TFA)) {
size_t sz = X86_PMC_IDX_MAX * sizeof(struct event_constraint);

cpuc->constraint_list = kzalloc_node(sz, GFP_KERNEL, cpu_to_node(cpu));
if (!cpuc->constraint_list)
goto err_shared_regs;
+ }

+ if (x86_pmu.flags & PMU_FL_EXCL_CNTRS) {
cpuc->excl_cntrs = allocate_excl_cntrs(cpu);
if (!cpuc->excl_cntrs)
goto err_constraint_list;
@@ -3564,9 +3619,10 @@ static void free_excl_cntrs(struct cpu_h
if (c->core_id == -1 || --c->refcnt == 0)
kfree(c);
cpuc->excl_cntrs = NULL;
- kfree(cpuc->constraint_list);
- cpuc->constraint_list = NULL;
}
+
+ kfree(cpuc->constraint_list);
+ cpuc->constraint_list = NULL;
}

static void intel_pmu_cpu_dying(int cpu)
@@ -4086,8 +4142,11 @@ static struct attribute *intel_pmu_caps_
NULL
};

+DEVICE_BOOL_ATTR(allow_tsx_force_abort, 0644, allow_tsx_force_abort);
+
static struct attribute *intel_pmu_attrs[] = {
&dev_attr_freeze_on_smi.attr,
+ NULL, /* &dev_attr_allow_tsx_force_abort.attr.attr */
NULL,
};

@@ -4580,6 +4639,15 @@ __init int intel_pmu_init(void)
tsx_attr = hsw_tsx_events_attrs;
intel_pmu_pebs_data_source_skl(
boot_cpu_data.x86_model == INTEL_FAM6_SKYLAKE_X);
+
+ if (boot_cpu_has(X86_FEATURE_TSX_FORCE_ABORT)) {
+ x86_pmu.flags |= PMU_FL_TFA;
+ x86_pmu.get_event_constraints = tfa_get_event_constraints;
+ x86_pmu.enable_all = intel_tfa_pmu_enable_all;
+ x86_pmu.commit_scheduling = intel_tfa_commit_scheduling;
+ intel_pmu_attrs[1] = &dev_attr_allow_tsx_force_abort.attr.attr;
+ }
+
pr_cont("Skylake events, ");
name = "skylake";
break;
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -243,6 +243,11 @@ struct cpu_hw_events {
int excl_thread_id; /* 0 or 1 */

/*
+ * SKL TSX_FORCE_ABORT shadow
+ */
+ u64 tfa_shadow;
+
+ /*
* AMD specific bits
*/
struct amd_nb *amd_nb;
@@ -681,6 +686,7 @@ do { \
#define PMU_FL_EXCL_CNTRS 0x4 /* has exclusive counter requirements */
#define PMU_FL_EXCL_ENABLED 0x8 /* exclusive counter active */
#define PMU_FL_PEBS_ALL 0x10 /* all events are valid PEBS events */
+#define PMU_FL_TFA 0x20 /* deal with TSX force abort */

#define EVENT_VAR(_id) event_attr_##_id
#define EVENT_PTR(_id) &event_attr_##_id.attr.attr