KVM: PPC: Book 3S: XICS: Implement ICS P/Q states

This patch implements P(Presented)/Q(Queued) states for ICS irqs.

When the interrupt is presented, set P. Present if P was not set.
If P is already set, don't present again, set Q.
When the interrupt is EOI'ed, move Q into P (and clear Q). If it is
set, re-present.

The asserted flag used by LSI is also incorporated into the P bit.

When the irq state is saved, P/Q bits are also saved, they need some
qemu modifications to be recognized and passed around to be restored.
KVM_XICS_PENDING bit set and saved should also indicate
KVM_XICS_PRESENTED bit set and saved. But it is possible some old
code doesn't have/recognize the P bit, so when we restore, we set P
for PENDING bit, too.

The idea and much of the code come from Ben.

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/kvm/book3s_xics.h

@@ -31,16 +31,19 @@
 /* Priority value to use for disabling an interrupt */
 #define MASKED	0xff
 
+#define PQ_PRESENTED	1
+#define PQ_QUEUED	2
+
 /* State for one irq source */
 struct ics_irq_state {
 	u32 number;
 	u32 server;
+	u32 pq_state;
 	u8  priority;
 	u8  saved_priority;
 	u8  resend;
 	u8  masked_pending;
 	u8  lsi;		/* level-sensitive interrupt */
-	u8  asserted; /* Only for LSI */
 	u8  exists;
 	int intr_cpu;
 	u32 host_irq;