| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <YTs2MpaI7iofckJI@hirez.programming.kicks-ass.net>
Date: Fri, 10 Sep 2021 12:40:50 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Song Liu <songliubraving@...com>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org, acme@...nel.org,
mingo@...hat.com, kjain@...ux.ibm.com, kernel-team@...com,
John Fastabend <john.fastabend@...il.com>,
Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCH v6 bpf-next 1/3] perf: enable branch record for software
events
On Tue, Sep 07, 2021 at 01:28:00PM -0700, Song Liu wrote:
> +static int
> +intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries, unsigned int cnt)
> +{
> + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> + unsigned long flags;
> +
> + local_irq_save(flags);
> + intel_pmu_disable_all();
> + intel_pmu_lbr_read();
> + cnt = min_t(unsigned int, cnt, x86_pmu.lbr_nr);
> +
> + memcpy(entries, cpuc->lbr_entries, sizeof(struct perf_branch_entry) * cnt);
> + intel_pmu_enable_all(0);
> + local_irq_restore(flags);
> + return cnt;
> +}
So elsewhere you state:
+ /* Given we stop LBR in software, we will waste a few entries.
+ * But we should try to waste as few as possible entries. We are at
+ * about 11 on x86_64 systems.
+ * Add a check for < 15 so that we get heads-up when something
+ * changes and wastes too many entries.
+ */
+ ASSERT_LT(skel->bss->wasted_entries, 15, "check_wasted_entries");
Which is atrocious.. so I disassembled the new function to get horrible
crap. The below seems to cure that.
---
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2143,19 +2143,19 @@ static __initconst const u64 knl_hw_cach
* However, there are some cases which may change PEBS status, e.g. PMI
* throttle. The PEBS_ENABLE should be updated where the status changes.
*/
-static __always_inline void __intel_pmu_disable_all(void)
+static __always_inline void __intel_pmu_disable_all(bool bts)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, 0);
- if (test_bit(INTEL_PMC_IDX_FIXED_BTS, cpuc->active_mask))
+ if (bts && test_bit(INTEL_PMC_IDX_FIXED_BTS, cpuc->active_mask))
intel_pmu_disable_bts();
}
static __always_inline void intel_pmu_disable_all(void)
{
- __intel_pmu_disable_all();
+ __intel_pmu_disable_all(true);
intel_pmu_pebs_disable_all();
intel_pmu_lbr_disable_all();
}
@@ -2186,14 +2186,12 @@ static void intel_pmu_enable_all(int add
__intel_pmu_enable_all(added, false);
}
-static int
-intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries, unsigned int cnt)
+static noinline int
+__intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries,
+ unsigned int cnt, unsigned long flags)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
- unsigned long flags;
- local_irq_save(flags);
- intel_pmu_disable_all();
intel_pmu_lbr_read();
cnt = min_t(unsigned int, cnt, x86_pmu.lbr_nr);
@@ -2203,6 +2201,36 @@ intel_pmu_snapshot_branch_stack(struct p
return cnt;
}
+static int
+intel_pmu_snapshot_branch_stack(struct perf_branch_entry *entries, unsigned int cnt)
+{
+ unsigned long flags;
+
+ /* must not have branches... */
+ local_irq_save(flags);
+ __intel_pmu_disable_all(false); /* we don't care about BTS */
+ __intel_pmu_pebs_disable_all();
+ __intel_pmu_lbr_disable();
+ /* ... until here */
+
+ return __intel_pmu_snapshot_branch_stack(entries, cnt, flags);
+}
+
+static int
+intel_pmu_snapshot_arch_branch_stack(struct perf_branch_entry *entries, unsigned int cnt)
+{
+ unsigned long flags;
+
+ /* must not have branches... */
+ local_irq_save(flags);
+ __intel_pmu_disable_all(false); /* we don't care about BTS */
+ __intel_pmu_pebs_disable_all();
+ __intel_pmu_arch_lbr_disable();
+ /* ... until here */
+
+ return __intel_pmu_snapshot_branch_stack(entries, cnt, flags);
+}
+
/*
* Workaround for:
* Intel Errata AAK100 (model 26)
@@ -2946,7 +2974,7 @@ static int intel_pmu_handle_irq(struct p
apic_write(APIC_LVTPC, APIC_DM_NMI);
intel_bts_disable_local();
cpuc->enabled = 0;
- __intel_pmu_disable_all();
+ __intel_pmu_disable_all(true);
handled = intel_pmu_drain_bts_buffer();
handled += intel_bts_interrupt();
status = intel_pmu_get_status();
@@ -6304,9 +6332,15 @@ __init int intel_pmu_init(void)
pr_cont("%d-deep LBR, ", x86_pmu.lbr_nr);
/* only support branch_stack snapshot for perfmon >= v2 */
- if (x86_pmu.disable_all == intel_pmu_disable_all)
- static_call_update(perf_snapshot_branch_stack,
- intel_pmu_snapshot_branch_stack);
+ if (x86_pmu.disable_all == intel_pmu_disable_all) {
+ if (boot_cpu_has(X86_FEATURE_ARCH_LBR)) {
+ static_call_update(perf_snapshot_branch_stack,
+ intel_pmu_snapshot_arch_branch_stack);
+ } else {
+ static_call_update(perf_snapshot_branch_stack,
+ intel_pmu_snapshot_branch_stack);
+ }
+ }
}
intel_pmu_check_extra_regs(x86_pmu.extra_regs);
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1296,6 +1296,14 @@ void intel_pmu_pebs_enable_all(void)
wrmsrl(MSR_IA32_PEBS_ENABLE, cpuc->pebs_enabled);
}
+void intel_pmu_pebs_disable_all(void)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+
+ if (cpuc->pebs_enabled)
+ __intel_pmu_pebs_disable_all();
+}
+
static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -1240,12 +1240,23 @@ static inline bool intel_pmu_has_bts(str
return intel_pmu_has_bts_period(event, hwc->sample_period);
}
-static __always_inline void intel_pmu_pebs_disable_all(void)
+static __always_inline void __intel_pmu_pebs_disable_all(void)
{
- struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+ wrmsrl(MSR_IA32_PEBS_ENABLE, 0);
+}
- if (cpuc->pebs_enabled)
- wrmsrl(MSR_IA32_PEBS_ENABLE, 0);
+static __always_inline void __intel_pmu_arch_lbr_disable(void)
+{
+ wrmsrl(MSR_ARCH_LBR_CTL, 0);
+}
+
+static __always_inline void __intel_pmu_lbr_disable(void)
+{
+ u64 debugctl;
+
+ rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
+ debugctl &= ~(DEBUGCTLMSR_LBR | DEBUGCTLMSR_FREEZE_LBRS_ON_PMI);
+ wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
}
int intel_pmu_save_and_restart(struct perf_event *event);
@@ -1322,6 +1333,8 @@ void intel_pmu_pebs_disable(struct perf_
void intel_pmu_pebs_enable_all(void);
+void intel_pmu_pebs_disable_all(void);
+
void intel_pmu_pebs_sched_task(struct perf_event_context *ctx, bool sched_in);
void intel_pmu_auto_reload_read(struct perf_event *event);
Powered by blists - more mailing lists