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Two perf fixes:

Browse Source 
- Do not check the LBR_TOS MSR when setting up unrelated LBR MSRs as this
    can cause malfunction when TOS is not supported.
 
  - Allocate the LBR XSAVE buffers along with the DS buffers upfront because
    allocating them when adding an event can deadlock.
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Merge tag 'perf-urgent-2021-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perf fixes from Thomas Gleixner:
 "Two perf fixes:

   - Do not check the LBR_TOS MSR when setting up unrelated LBR MSRs as
     this can cause malfunction when TOS is not supported

   - Allocate the LBR XSAVE buffers along with the DS buffers upfront
     because allocating them when adding an event can deadlock"

* tag 'perf-urgent-2021-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/lbr: Remove cpuc->lbr_xsave allocation from atomic context
  perf/x86: Avoid touching LBR_TOS MSR for Arch LBR
This commit is contained in:
Linus Torvalds 2021-05-23 06:32:40 -10:00
commit 6ebb6814a1
4 changed files with 31 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/x86/events/core.c
View File

@ -396,10 +396,12 @@ int x86_reserve_hardware(void)
if (!atomic_inc_not_zero(&pmc_refcount)) {
mutex_lock(&pmc_reserve_mutex);
if (atomic_read(&pmc_refcount) == 0) {
if (!reserve_pmc_hardware())
if (!reserve_pmc_hardware()) {
err = -EBUSY;
else
} else {
reserve_ds_buffers();
reserve_lbr_buffers();
}
}
if (!err)
atomic_inc(&pmc_refcount);

2
arch/x86/events/intel/core.c
View File

@ -6253,7 +6253,7 @@ __init int intel_pmu_init(void)
* Check all LBT MSR here.
* Disable LBR access if any LBR MSRs can not be accessed.
*/
if (x86_pmu.lbr_nr && !check_msr(x86_pmu.lbr_tos, 0x3UL))
if (x86_pmu.lbr_tos && !check_msr(x86_pmu.lbr_tos, 0x3UL))
x86_pmu.lbr_nr = 0;
for (i = 0; i < x86_pmu.lbr_nr; i++) {
if (!(check_msr(x86_pmu.lbr_from + i, 0xffffUL) &&

26
arch/x86/events/intel/lbr.c
View File

@ -658,7 +658,6 @@ static inline bool branch_user_callstack(unsigned br_sel)
void intel_pmu_lbr_add(struct perf_event *event)
{
struct kmem_cache *kmem_cache = event->pmu->task_ctx_cache;
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
if (!x86_pmu.lbr_nr)
@ -696,11 +695,6 @@ void intel_pmu_lbr_add(struct perf_event *event)
perf_sched_cb_inc(event->ctx->pmu);
if (!cpuc->lbr_users++ && !event->total_time_running)
intel_pmu_lbr_reset();
if (static_cpu_has(X86_FEATURE_ARCH_LBR) &&
kmem_cache && !cpuc->lbr_xsave &&
(cpuc->lbr_users != cpuc->lbr_pebs_users))
cpuc->lbr_xsave = kmem_cache_alloc(kmem_cache, GFP_KERNEL);
}
void release_lbr_buffers(void)
@ -722,6 +716,26 @@ void release_lbr_buffers(void)
}
}
void reserve_lbr_buffers(void)
{
struct kmem_cache *kmem_cache;
struct cpu_hw_events *cpuc;
int cpu;
if (!static_cpu_has(X86_FEATURE_ARCH_LBR))
return;
for_each_possible_cpu(cpu) {
cpuc = per_cpu_ptr(&cpu_hw_events, cpu);
kmem_cache = x86_get_pmu(cpu)->task_ctx_cache;
if (!kmem_cache || cpuc->lbr_xsave)
continue;
cpuc->lbr_xsave = kmem_cache_alloc_node(kmem_cache, GFP_KERNEL,
cpu_to_node(cpu));
}
}
void intel_pmu_lbr_del(struct perf_event *event)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);

6
arch/x86/events/perf_event.h
View File

@ -1244,6 +1244,8 @@ void reserve_ds_buffers(void);
void release_lbr_buffers(void);
void reserve_lbr_buffers(void);
extern struct event_constraint bts_constraint;
extern struct event_constraint vlbr_constraint;
@ -1393,6 +1395,10 @@ static inline void release_lbr_buffers(void)
{
}
static inline void reserve_lbr_buffers(void)
{
}
static inline int intel_pmu_init(void)
{
return 0;