perfcounters: provide expansion room in the ABI

Impact: ABI change

This expands several fields in the perf_counter_hw_event struct and adds
a "flags" argument to the perf_counter_open system call, in order that
features can be added in future without ABI changes.

In particular the record_type field is expanded to 64 bits, and the
space for flag bits has been expanded from 32 to 64 bits.

This also adds some new fields:

* read_format (64 bits) is intended to provide a way to specify what
  userspace wants to get back when it does a read() on a simple
  (non-interrupting) counter;

* exclude_idle (1 bit) provides a way for userspace to ask that events
  that occur when the cpu is idle be excluded;

* extra_config_len will provide a way for userspace to supply an
  arbitrary amount of extra machine-specific PMU configuration data
  immediately following the perf_counter_hw_event struct, to allow
  sophisticated users to program things such as instruction matching
  CAMs and address range registers;

* __reserved_3 and __reserved_4 provide space for future expansion.

Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 9 insertions, 3 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 186efaf49665..c42455ab1558 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -69,9 +69,10 @@ struct perf_counter_hw_event {
         __s64                   type;
 
         __u64                   irq_period;
-        __u32                   record_type;
+        __u64                   record_type;
+        __u64                   read_format;
 
-        __u32                   disabled       :  1, /* off by default        */
+        __u64                   disabled       :  1, /* off by default        */
                                 nmi            :  1, /* NMI sampling          */
                                 raw            :  1, /* raw event type        */
                                 inherit        :  1, /* children inherit it   */
@@ -80,10 +81,15 @@ struct perf_counter_hw_event {
                                 exclude_user   :  1, /* don't count user      */
                                 exclude_kernel :  1, /* ditto kernel          */
                                 exclude_hv     :  1, /* ditto hypervisor      */
+                                exclude_idle   :  1, /* don't count when idle */
 
-                                __reserved_1 : 23;
+                                __reserved_1 : 55;
+
+        __u32                   extra_config_len;
+        __u32                   __reserved_4;
 
         __u64                   __reserved_2;
+        __u64                   __reserved_3;
 };
 
 /*