linux-kernel - [PATCH] perf/x86/intel: Add cpu_(prepare|starting|dying) for core

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Message-Id: <1429606465-10271-1-git-send-email-jolsa@kernel.org>
Date:	Tue, 21 Apr 2015 10:54:25 +0200
From:	Jiri Olsa <jolsa@...nel.org>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stephane Eranian <eranian@...gle.com>
Subject: [PATCH] perf/x86/intel: Add cpu_(prepare|starting|dying) for core_pmu

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 <jolsa@...nel.org>
---
 arch/x86/kernel/cpu/perf_event_intel.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 9da2400c2ec3..0a61a9a021de 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -2533,6 +2533,10 @@ ssize_t intel_event_sysfs_show(char *page, u64 config)
 	return x86_event_sysfs_show(page, config, event);
 }
 
+static int  intel_pmu_cpu_prepare(int cpu);
+static void intel_pmu_cpu_starting(int cpu);
+static void intel_pmu_cpu_dying(int cpu);
+
 static __initconst const struct x86_pmu core_pmu = {
 	.name			= "core",
 	.handle_irq		= x86_pmu_handle_irq,
@@ -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,
+	.cpu_prepare		= intel_pmu_cpu_prepare,
+	.cpu_starting		= intel_pmu_cpu_starting,
+	.cpu_dying		= intel_pmu_cpu_dying,
 };
 
 struct intel_shared_regs *allocate_shared_regs(int cpu)
-- 
1.9.3

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