s390/cpumf: Support for CPU Measurement Sampling Facility LS bit

Adds support for the CPU Measurement Sampling Facility limit sampling
bit in the sampling device driver.
Limited samples have no valueable information are not collected.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: Thomas Richter

arch/s390/include/asm/cpu_mf.h

@@ -109,7 +109,9 @@ struct hws_basic_entry {
 	unsigned int AS:2;	    /* 29-30 PSW address-space control	 */
 	unsigned int I:1;	    /* 31 entry valid or invalid	 */
 	unsigned int CL:2;	    /* 32-33 Configuration Level	 */
-	unsigned int:14;
+	unsigned int H:1;	    /* 34 Host Indicator		 */
+	unsigned int LS:1;	    /* 35 Limited Sampling		 */
+	unsigned int:12;
 	unsigned int prim_asn:16;   /* primary ASN			 */
 	unsigned long long ia;	    /* Instruction Address		 */
 	unsigned long long gpp;     /* Guest Program Parameter		 */

arch/s390/kernel/perf_cpum_sf.c

@@ -1179,7 +1179,7 @@ static void hw_collect_samples(struct perf_event *event, unsigned long *sdbt,
 	sample = (struct hws_basic_entry *) *sdbt;
 	while ((unsigned long *) sample < (unsigned long *) te) {
 		/* Check for an empty sample */
-		if (!sample->def)
+		if (!sample->def || sample->LS)
 			break;
 
 		/* Update perf event period */