On Tue, Apr 21, 2015 at 05:18:27PM +0200, Jiri Olsa wrote:
> On Tue, Apr 21, 2015 at 05:12:16PM +0200, Peter Zijlstra wrote:
> > On Tue, Apr 21, 2015 at 10:54:25AM +0200, Jiri Olsa wrote:
> > > @@ -2559,6 +2563,9 @@ static __initconst const struct x86_pmu core_pmu = {
> > > .guest_get_msrs = core_guest_get_msrs,
> > > .format_attrs = intel_arch_formats_attr,
> > > .events_sysfs_show = intel_event_sysfs_show,
> >
> > Could you also insert a little comment here how these methods are for
> > 'funny' 'hardware' ?
>
> ook, will do v3
attached,
jirka
---
The core_pmu does not define cpu_* callbacks, which handles
allocation of 'struct cpu_hw_events::shared_regs' data,
initialization of debug store and PMU_FL_EXCL_CNTRS counters.
While this probably won't happen on bare metal, virtual CPU can
define x86_pmu.extra_regs together with PMU version 1 and thus
be using core_pmu -> using shared_regs data without it being
allocated. That could could leave to following panic:
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff8152cd4f>] _spin_lock_irqsave+0x1f/0x40
SNIP
[<ffffffff81024bd9>] __intel_shared_reg_get_constraints+0x69/0x1e0
[<ffffffff81024deb>] intel_get_event_constraints+0x9b/0x180
[<ffffffff8101e815>] x86_schedule_events+0x75/0x1d0
[<ffffffff810586dc>] ? check_preempt_curr+0x7c/0x90
[<ffffffff810649fe>] ? try_to_wake_up+0x24e/0x3e0
[<ffffffff81064ba2>] ? default_wake_function+0x12/0x20
[<ffffffff8109eb16>] ? autoremove_wake_function+0x16/0x40
[<ffffffff810577e9>] ? __wake_up_common+0x59/0x90
[<ffffffff811a9517>] ? __d_lookup+0xa7/0x150
[<ffffffff8119db5f>] ? do_lookup+0x9f/0x230
[<ffffffff811a993a>] ? dput+0x9a/0x150
[<ffffffff8119c8f5>] ? path_to_nameidata+0x25/0x60
[<ffffffff8119e90a>] ? __link_path_walk+0x7da/0x1000
[<ffffffff8101d8f9>] ? x86_pmu_add+0xb9/0x170
[<ffffffff8101d7a7>] x86_pmu_commit_txn+0x67/0xc0
[<ffffffff811b07b0>] ? mntput_no_expire+0x30/0x110
[<ffffffff8119c731>] ? path_put+0x31/0x40
[<ffffffff8107c297>] ? current_fs_time+0x27/0x30
[<ffffffff8117d170>] ? mem_cgroup_get_reclaim_stat_from_page+0x20/0x70
[<ffffffff8111b7aa>] group_sched_in+0x13a/0x170
[<ffffffff81014a29>] ? sched_clock+0x9/0x10
[<ffffffff8111bac8>] ctx_sched_in+0x2e8/0x330
[<ffffffff8111bb7b>] perf_event_sched_in+0x6b/0xb0
[<ffffffff8111bc36>] perf_event_context_sched_in+0x76/0xc0
[<ffffffff8111eb3b>] perf_event_comm+0x1bb/0x2e0
[<ffffffff81195ee9>] set_task_comm+0x69/0x80
[<ffffffff81195fe1>] setup_new_exec+0xe1/0x2e0
[<ffffffff811ea68e>] load_elf_binary+0x3ce/0x1ab0
Adding cpu_(prepare|starting|dying) for core_pmu to have shared_regs
data allocated for core_pmu. AFAICS there's no harm to initialize
debug store and PMU_FL_EXCL_CNTRS either for core_pmu.
Signed-off-by: Jiri Olsa <[email protected]>
---
arch/x86/kernel/cpu/perf_event_intel.c | 66 +++++++++++++++++++---------------
1 file changed, 38 insertions(+), 28 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c
b/arch/x86/kernel/cpu/perf_event_intel.c
index 9da2400c2ec3..8a4e21eb2087 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -2533,34 +2533,6 @@ ssize_t intel_event_sysfs_show(char *page, u64 config)
return x86_event_sysfs_show(page, config, event);
}
-static __initconst const struct x86_pmu core_pmu = {
- .name = "core",
- .handle_irq = x86_pmu_handle_irq,
- .disable_all = x86_pmu_disable_all,
- .enable_all = core_pmu_enable_all,
- .enable = core_pmu_enable_event,
- .disable = x86_pmu_disable_event,
- .hw_config = x86_pmu_hw_config,
- .schedule_events = x86_schedule_events,
- .eventsel = MSR_ARCH_PERFMON_EVENTSEL0,
- .perfctr = MSR_ARCH_PERFMON_PERFCTR0,
- .event_map = intel_pmu_event_map,
- .max_events = ARRAY_SIZE(intel_perfmon_event_map),
- .apic = 1,
- /*
- * Intel PMCs cannot be accessed sanely above 32 bit width,
- * so we install an artificial 1<<31 period regardless of
- * the generic event period:
- */
- .max_period = (1ULL << 31) - 1,
- .get_event_constraints = intel_get_event_constraints,
- .put_event_constraints = intel_put_event_constraints,
- .event_constraints = intel_core_event_constraints,
- .guest_get_msrs = core_guest_get_msrs,
- .format_attrs = intel_arch_formats_attr,
- .events_sysfs_show = intel_event_sysfs_show,
-};
-
struct intel_shared_regs *allocate_shared_regs(int cpu)
{
struct intel_shared_regs *regs;
@@ -2743,6 +2715,44 @@ static struct attribute *intel_arch3_formats_attr[] = {
NULL,
};
+static __initconst const struct x86_pmu core_pmu = {
+ .name = "core",
+ .handle_irq = x86_pmu_handle_irq,
+ .disable_all = x86_pmu_disable_all,
+ .enable_all = core_pmu_enable_all,
+ .enable = core_pmu_enable_event,
+ .disable = x86_pmu_disable_event,
+ .hw_config = x86_pmu_hw_config,
+ .schedule_events = x86_schedule_events,
+ .eventsel = MSR_ARCH_PERFMON_EVENTSEL0,
+ .perfctr = MSR_ARCH_PERFMON_PERFCTR0,
+ .event_map = intel_pmu_event_map,
+ .max_events = ARRAY_SIZE(intel_perfmon_event_map),
+ .apic = 1,
+ /*
+ * Intel PMCs cannot be accessed sanely above 32 bit width,
+ * so we install an artificial 1<<31 period regardless of
+ * the generic event period:
+ */
+ .max_period = (1ULL << 31) - 1,
+ .get_event_constraints = intel_get_event_constraints,
+ .put_event_constraints = intel_put_event_constraints,
+ .event_constraints = intel_core_event_constraints,
+ .guest_get_msrs = core_guest_get_msrs,
+ .format_attrs = intel_arch_formats_attr,
+ .events_sysfs_show = intel_event_sysfs_show,
+
+ /*
+ * Virtual (or funny metal) CPU can define x86_pmu.extra_regs
+ * together with PMU version 1 and thus be using core_pmu with
+ * shared_regs. We need following callbacks here to allocate
+ * it properly.
+ */
+ .cpu_prepare = intel_pmu_cpu_prepare,
+ .cpu_starting = intel_pmu_cpu_starting,
+ .cpu_dying = intel_pmu_cpu_dying,
+};
+
static __initconst const struct x86_pmu intel_pmu = {
.name = "Intel",
.handle_irq = intel_pmu_handle_irq,
--
1.9.3
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