KVM: s390: use pid of cpu thread for sampling tagging

Right now we use the address of the sie control block as tag for
the sampling data. This is hard to get for users. Let's just use
the PID of the cpu thread to mark the hardware samples.

Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/entry.S

@@ -199,7 +199,7 @@ ENTRY(sie64a)
 	jo	.Lsie_skip			# exit if fp/vx regs changed
 	tm	__LC_MACHINE_FLAGS+6,0x20	# MACHINE_FLAG_LPP
 	jz	.Lsie_enter
-	.insn	s,0xb2800000,__SF_EMPTY(%r15)	# set guest id
+	.insn	s,0xb2800000,__LC_CURRENT_PID	# set guest id to pid
 .Lsie_enter:
 	sie	0(%r14)
 	tm	__LC_MACHINE_FLAGS+6,0x20	# MACHINE_FLAG_LPP

arch/s390/kernel/perf_cpum_sf.c

@@ -1019,12 +1019,9 @@ static int perf_push_sample(struct perf_event *event, struct sf_raw_sample *sfr)
 		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.
+	/* The host-program-parameter (hpp) contains the pid of
+	 * the CPU thread as set by sie64a() in entry.S.
+	 * If non-zero assume a guest sample.
 	 */
 	if (sfr->basic.hpp)
 		sde_regs->in_guest = 1;