powerpc/perf: Core EBB support for 64-bit book3s
Add support for EBB (Event Based Branches) on 64-bit book3s. See the
included documentation for more details.
EBBs are a feature which allows the hardware to branch directly to a
specified user space address when a PMU event overflows. This can be
used by programs for self-monitoring with no kernel involvement in the
inner loop.
Most of the logic is in the generic book3s code, primarily to avoid a
proliferation of PMU callbacks.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
index 200d763..49a13e0 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -67,4 +67,18 @@
}
#endif
+static inline void clear_task_ebb(struct task_struct *t)
+{
+#ifdef CONFIG_PPC_BOOK3S_64
+ /* EBB perf events are not inherited, so clear all EBB state. */
+ t->thread.bescr = 0;
+ t->thread.mmcr2 = 0;
+ t->thread.mmcr0 = 0;
+ t->thread.siar = 0;
+ t->thread.sdar = 0;
+ t->thread.sier = 0;
+ t->thread.used_ebb = 0;
+#endif
+}
+
#endif /* _ASM_POWERPC_SWITCH_TO_H */