powerpc/pseries: Add dispatch dispersion statistics

PHYP tells us how often a shared processor dispatch changed physical cpus.
This can highlight performance problems caused by the hypervisor.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h
index 68235f7..d2a65e8 100644
--- a/arch/powerpc/include/asm/lppaca.h
+++ b/arch/powerpc/include/asm/lppaca.h
@@ -125,7 +125,7 @@
 	// NOTE: This value will ALWAYS be zero for dedicated processors and
 	// will NEVER be zero for shared processors (ie, initialized to a 1).
 	volatile u32 yield_count;	// PLIC increments each dispatchx00-x03
-	u32 reserved6;
+	volatile u32 dispersion_count;	// dispatch changed phys cpu    x04-x07
 	volatile u64 cmo_faults;	// CMO page fault count         x08-x0F
 	volatile u64 cmo_fault_time;	// CMO page fault time          x10-x17
 	u8	reserved7[104];		// Reserved                     x18-x7F