4 files changed, 38 insertions, 13 deletions

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 8355c84b9729..a9c606bb4945 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1883,9 +1883,9 @@ static struct pmu pmu = {
 
 void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
 {
-        userpg->cap_usr_time = 0;
-        userpg->cap_usr_time_zero = 0;
-        userpg->cap_usr_rdpmc = x86_pmu.attr_rdpmc;
+        userpg->cap_user_time = 0;
+        userpg->cap_user_time_zero = 0;
+        userpg->cap_user_rdpmc = x86_pmu.attr_rdpmc;
         userpg->pmc_width = x86_pmu.cntval_bits;
 
         if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
@@ -1894,13 +1894,13 @@ void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
         if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
                 return;
 
-        userpg->cap_usr_time = 1;
+        userpg->cap_user_time = 1;
         userpg->time_mult = this_cpu_read(cyc2ns);
         userpg->time_shift = CYC2NS_SCALE_FACTOR;
         userpg->time_offset = this_cpu_read(cyc2ns_offset) - now;
 
         if (sched_clock_stable && !check_tsc_disabled()) {
-                userpg->cap_usr_time_zero = 1;
+                userpg->cap_user_time_zero = 1;
                 userpg->time_zero = this_cpu_read(cyc2ns_offset);
         }
 }
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 7f6d584c267b..009a655a5d35 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -380,10 +380,13 @@ struct perf_event_mmap_page {
         union {
                 __u64   capabilities;
                 struct {
-                        __u64   cap_usr_time            : 1,
-                                cap_usr_rdpmc           : 1,
-                                cap_usr_time_zero       : 1,
-                                cap_____res             : 61;
+                        __u64   cap_bit0                : 1, /* Always 0, deprecated, see commit 860f085b74e9 */
+                                cap_bit0_is_deprecated  : 1, /* Always 1, signals that bit 0 is zero */
+
+                                cap_user_rdpmc          : 1, /* The RDPMC instruction can be used to read counts */
+                                cap_user_time           : 1, /* The time_* fields are used */
+                                cap_user_time_zero      : 1, /* The time_zero field is used */
+                                cap_____res             : 59;
                 };
         };
 
@@ -442,12 +445,13 @@ struct perf_event_mmap_page {
          *               ((rem * time_mult) >> time_shift);
          */
         __u64   time_zero;
+        __u32   size;                   /* Header size up to __reserved[] fields. */
 
                 /*
                  * Hole for extension of the self monitor capabilities
                  */
 
-        __u64   __reserved[119];        /* align to 1k */
+        __u8    __reserved[118*8+4];    /* align to 1k. */
 
         /*
          * Control data for the mmap() data buffer.
diff --git a/kernel/events/core.c b/kernel/events/core.c
index dd236b66ca3a..cb4238e85b38 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3660,6 +3660,26 @@ static void calc_timer_values(struct perf_event *event,
         *running = ctx_time - event->tstamp_running;
 }
 
+static void perf_event_init_userpage(struct perf_event *event)
+{
+        struct perf_event_mmap_page *userpg;
+        struct ring_buffer *rb;
+
+        rcu_read_lock();
+        rb = rcu_dereference(event->rb);
+        if (!rb)
+                goto unlock;
+
+        userpg = rb->user_page;
+
+        /* Allow new userspace to detect that bit 0 is deprecated */
+        userpg->cap_bit0_is_deprecated = 1;
+        userpg->size = offsetof(struct perf_event_mmap_page, __reserved);
+
+unlock:
+        rcu_read_unlock();
+}
+
 void __weak arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
 {
 }
@@ -4044,6 +4064,7 @@ again:
         ring_buffer_attach(event, rb);
         rcu_assign_pointer(event->rb, rb);
 
+        perf_event_init_userpage(event);
         perf_event_update_userpage(event);
 
 unlock:
diff --git a/tools/perf/arch/x86/util/tsc.c b/tools/perf/arch/x86/util/tsc.c
index 9570c2b0f83c..b2519e49424f 100644
--- a/tools/perf/arch/x86/util/tsc.c
+++ b/tools/perf/arch/x86/util/tsc.c
@@ -32,7 +32,7 @@ u64 tsc_to_perf_time(u64 cyc, struct perf_tsc_conversion *tc)
 int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
                              struct perf_tsc_conversion *tc)
 {
-        bool cap_usr_time_zero;
+        bool cap_user_time_zero;
         u32 seq;
         int i = 0;
 
@@ -42,7 +42,7 @@ int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
                 tc->time_mult = pc->time_mult;
                 tc->time_shift = pc->time_shift;
                 tc->time_zero = pc->time_zero;
-                cap_usr_time_zero = pc->cap_usr_time_zero;
+                cap_user_time_zero = pc->cap_user_time_zero;
                 rmb();
                 if (pc->lock == seq && !(seq & 1))
                         break;
@@ -52,7 +52,7 @@ int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
                 }
         }
 
-        if (!cap_usr_time_zero)
+        if (!cap_user_time_zero)
                 return -EOPNOTSUPP;
 
         return 0;