perf/x86/amd/lbr: Add LbrExtV2 branch record support

If AMD Last Branch Record Extension Version 2 (LbrExtV2) is detected,
enable it alongside LBR Freeze on PMI when an event requests branch stack
i.e. PERF_SAMPLE_BRANCH_STACK.

Each branch record is represented by a pair of registers, LBR From and LBR
To. The freeze feature prevents any updates to these registers once a PMC
overflows. The contents remain unchanged until the freeze bit is cleared by
the PMI handler.

The branch records are read and copied to sample data before unfreezing.
However, only valid entries are copied. There is no additional register to
denote which of the register pairs represent the top of the stack (TOS)
since internal register renaming always ensures that the first pair (i.e.
index 0) is the one representing the most recent branch and so on.

The LBR registers are per-thread resources and are cleared explicitly
whenever a new task is scheduled in. There are no special implications on
the contents of these registers when transitioning to deep C-states.

Signed-off-by: Sandipan Das <sandipan.das@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/d3b8500a3627a0d4d0259b005891ee248f248d91.1660211399.git.sandipan.das@amd.com

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 82e8a6d87ade..e8930414cba5 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -1233,6 +1233,14 @@ static inline bool fixed_counter_disabled(int i, struct pmu *pmu)
 int amd_pmu_init(void);
 
 int amd_pmu_lbr_init(void);
+void amd_pmu_lbr_reset(void);
+void amd_pmu_lbr_read(void);
+void amd_pmu_lbr_add(struct perf_event *event);
+void amd_pmu_lbr_del(struct perf_event *event);
+void amd_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in);
+void amd_pmu_lbr_enable_all(void);
+void amd_pmu_lbr_disable_all(void);
+int amd_pmu_lbr_hw_config(struct perf_event *event);
 
 #ifdef CONFIG_PERF_EVENTS_AMD_BRS