powerpc/powernv: Set the PTCR for the Nest MMU

The Nest MMU manages address translation for accelerators on the POWER9.  To
do so, it needs a page table, so export the system page table to the Nest
MMU.  This will quietly fail on pre-POWER9 systems that do not have a NMMU.

The NMMU is currently unused, so this change is currently effectively a NOP,
but the NMMU and VAS will eventually be used.

sys/powerpc/powernv/opal.h

@@ -91,6 +91,7 @@ int opal_call(uint64_t token, ...);
 #define	OPAL_INT_EOI			124
 #define	OPAL_INT_SET_MFRR		125
 #define	OPAL_PCI_TCE_KILL		126
+#define	OPAL_NMMU_SET_PTCR		127
 #define	OPAL_XIVE_RESET			128
 #define	OPAL_XIVE_GET_IRQ_INFO		129
 #define	OPAL_XIVE_GET_IRQ_CONFIG	130

sys/powerpc/powernv/platform_powernv.c

@@ -494,3 +494,14 @@ static void
 powernv_cpu_idle(sbintime_t sbt)
 {
 }
+
+/* Set up the Nest MMU on POWER9 relatively early, but after pmap is setup. */
+static void
+powernv_setup_nmmu(void *unused)
+{
+	if (opal_check() != 0)
+		return;
+	opal_call(OPAL_NMMU_SET_PTCR, -1, mfspr(SPR_PTCR));
+}
+
+SYSINIT(powernv_setup_nmmu, SI_SUB_CPU, SI_ORDER_ANY, powernv_setup_nmmu, NULL);