s390/cpum_sf: Dynamically extend the sampling buffer if overflows occur

Improve the sampling buffer allocation and add a function to reallocate and
increase the sampling buffer structure.  The number of allocated buffer elements
(sample-data-blocks) are accounted.  You can control the minimum and maximum
number these sample-data-blocks through the cpum_sfb_size kernel parameter.

The number hardware sample overflows (if any) are also accounted and stored
per perf event.  During the PMU disable/enable calls, the accumulated overflow
counter is analyzed and, if necessary, the sampling buffer is dynamically
increased.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/perf_event.h

@@ -49,6 +49,10 @@ extern unsigned long perf_misc_flags(struct pt_regs *regs);
 #define PERF_CPUM_SF_MAX_CTR		1
 #define PERF_EVENT_CPUM_SF		0xB0000UL	/* Raw event ID */
 
+#define REG_NONE		0
+#define REG_OVERFLOW		1
+#define OVERFLOW_REG(hwc)	((hwc)->extra_reg.config)
+#define SFB_ALLOC_REG(hwc)	((hwc)->extra_reg.alloc)
 #define TEAR_REG(hwc)		((hwc)->last_tag)
 #define SAMPL_RATE(hwc)		((hwc)->event_base)