s390/cpum_sf: Detect KVM guest samples

The host-program-parameter (hpp) value of basic sample-data-entries designates
a SIE control block that is set by the LPP instruction in sie64a().
Non-zero values indicate guest samples, a value of zero indicates a host sample.

For perf samples, host and guest samples are distinguished using particular
PERF_MISC_* flags.  The perf layer calls perf_misc_flags() to set the flags
based on the pt_regs content.  For each sample-data-entry, the cpum_sf PMU
creates a pt_regs structure with the sample-data information.  An additional
flag structure is added to easily distinguish between host and guest samples.

Signed-off-by: Hendrik Brueckner <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>

Author: hbrueckner

arch/s390/include/asm/perf_event.h

@@ -42,6 +42,12 @@ 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)
 
+/* Perf pt_regs extension for sample-data-entry indicators */
+struct perf_sf_sde_regs {
+	unsigned char in_guest:1;	  /* guest sample */
+	unsigned long reserved:63;	  /* reserved */
+};
+
 /* Perf PMU definitions for the counter facility */
 #define PERF_CPUM_CF_MAX_CTR		256
 

arch/s390/kernel/perf_cpum_sf.c

@@ -840,6 +840,7 @@ static int perf_push_sample(struct perf_event *event,
 {
 	int overflow;
 	struct pt_regs regs;
+	struct perf_sf_sde_regs *sde_regs;
 	struct perf_sample_data data;
 
 	/* Skip samples that are invalid or for which the instruction address
@@ -850,7 +851,16 @@ static int perf_push_sample(struct perf_event *event,
 
 	perf_sample_data_init(&data, 0, event->hw.last_period);
 
+	/* Setup pt_regs to look like an CPU-measurement external interrupt
+	 * using the Program Request Alert code.  The regs.int_parm_long
+	 * field which is unused contains additional sample-data-entry related
+	 * indicators.
+	 */
 	memset(&regs, 0, sizeof(regs));
+	regs.int_code = 0x1407;
+	regs.int_parm = CPU_MF_INT_SF_PRA;
+	sde_regs = (struct perf_sf_sde_regs *) &regs.int_parm_long;
+
 	regs.psw.addr = sample->ia;
 	if (sample->T)
 		regs.psw.mask |= PSW_MASK_DAT;
@@ -873,6 +883,16 @@ static int perf_push_sample(struct perf_event *event,
 		break;
 	}
 
+	/* The host-program-parameter (hpp) contains the sie control
+	 * block that is set by sie64a() in entry64.S.	Check if hpp
+	 * refers to a valid control block and set sde_regs flags
+	 * accordingly.  This would allow to use hpp values for other
+	 * purposes too.
+	 * For now, simply use a non-zero value as guest indicator.
+	 */
+	if (sample->hpp)
+		sde_regs->in_guest = 1;
+
 	overflow = 0;
 	if (perf_event_overflow(event, &data, &regs)) {
 		overflow = 1;

arch/s390/kernel/perf_event.c

@@ -1,7 +1,7 @@
 /*
  * Performance event support for s390x
  *
- *  Copyright IBM Corp. 2012
+ *  Copyright IBM Corp. 2012, 2013
  *  Author(s): Hendrik Brueckner <[email protected]>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -89,8 +89,31 @@ static unsigned long perf_misc_guest_flags(struct pt_regs *regs)
 					: PERF_RECORD_MISC_GUEST_KERNEL;
 }
 
+static unsigned long perf_misc_flags_sf(struct pt_regs *regs)
+{
+	struct perf_sf_sde_regs *sde_regs;
+	unsigned long flags;
+
+	sde_regs = (struct perf_sf_sde_regs *) &regs->int_parm_long;
+	if (sde_regs->in_guest)
+		flags = user_mode(regs) ? PERF_RECORD_MISC_GUEST_USER
+					: PERF_RECORD_MISC_GUEST_KERNEL;
+	else
+		flags = user_mode(regs) ? PERF_RECORD_MISC_USER
+					: PERF_RECORD_MISC_KERNEL;
+	return flags;
+}
+
 unsigned long perf_misc_flags(struct pt_regs *regs)
 {
+	/* Check if the cpum_sf PMU has created the pt_regs structure.
+	 * In this case, perf misc flags can be easily extracted.  Otherwise,
+	 * do regular checks on the pt_regs content.
+	 */
+	if (regs->int_code == 0x1407 && regs->int_parm == CPU_MF_INT_SF_PRA)
+		if (!regs->gprs[15])
+			return perf_misc_flags_sf(regs);
+
 	if (is_in_guest(regs))
 		return perf_misc_guest_flags(regs);