ARM: perf: add guest vs host discrimination

Add minimal guest support to perf, so it can distinguish whether
the PMU interrupt was in the host or the guest, as well as collecting
some very basic information (guest PC, user vs kernel mode).

This is not feature complete though, as it doesn't support backtracing
in the guest.

Based on the x86 implementation, tested with KVM/ARM.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

2 files changed, 41 insertions, 0 deletions

diff --git a/arch/arm/include/asm/perf_event.h b/arch/arm/include/asm/perf_event.h
index 625cd621a436..00416edecead 100644
--- a/arch/arm/include/asm/perf_event.h
+++ b/arch/arm/include/asm/perf_event.h
@@ -21,4 +21,9 @@
 #define C(_x)                           PERF_COUNT_HW_CACHE_##_x
 #define CACHE_OP_UNSUPPORTED            0xFFFF
 
+struct pt_regs;
+extern unsigned long perf_instruction_pointer(struct pt_regs *regs);
+extern unsigned long perf_misc_flags(struct pt_regs *regs);
+#define perf_misc_flags(regs)   perf_misc_flags(regs)
+
 #endif /* __ARM_PERF_EVENT_H__ */
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 53c0304b734a..f8406af03279 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -576,6 +576,10 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
 {
         struct frame_tail __user *tail;
 
+        if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
+                /* We don't support guest os callchain now */
+                return;
+        }
 
         tail = (struct frame_tail __user *)regs->ARM_fp - 1;
 
@@ -603,9 +607,41 @@ perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
 {
         struct stackframe fr;
 
+        if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
+                /* We don't support guest os callchain now */
+                return;
+        }
+
         fr.fp = regs->ARM_fp;
         fr.sp = regs->ARM_sp;
         fr.lr = regs->ARM_lr;
         fr.pc = regs->ARM_pc;
         walk_stackframe(&fr, callchain_trace, entry);
 }
+
+unsigned long perf_instruction_pointer(struct pt_regs *regs)
+{
+        if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
+                return perf_guest_cbs->get_guest_ip();
+
+        return instruction_pointer(regs);
+}
+
+unsigned long perf_misc_flags(struct pt_regs *regs)
+{
+        int misc = 0;
+
+        if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
+                if (perf_guest_cbs->is_user_mode())
+                        misc |= PERF_RECORD_MISC_GUEST_USER;
+                else
+                        misc |= PERF_RECORD_MISC_GUEST_KERNEL;
+        } else {
+                if (user_mode(regs))
+                        misc |= PERF_RECORD_MISC_USER;
+                else
+                        misc |= PERF_RECORD_MISC_KERNEL;
+        }
+
+        return misc;
+}