ppc/xive: Assert group interrupts were redistributed

Add some assertions to try to ensure presented group interrupts do
not get lost without being redistributed, if they become precluded
by CPPR or preempted by a higher priority interrupt.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Glenn Miles <milesg@linux.ibm.com>
Reviewed-by: Michael Kowal <kowal@linux.ibm.com>
Tested-by: Gautam Menghani <gautam@linux.ibm.com>
Link: https://lore.kernel.org/qemu-devel/20250512031100.439842-40-npiggin@gmail.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/intc/xive.c

@@ -132,6 +132,8 @@ void xive_tctx_pipr_set(XiveTCTX *tctx, uint8_t ring, uint8_t pipr,
     uint8_t *sig_regs = xive_tctx_signal_regs(tctx, ring);
     uint8_t *regs = &tctx->regs[ring];
 
+    g_assert(!xive_nsr_indicates_group_exception(ring, sig_regs[TM_NSR]));
+
     sig_regs[TM_PIPR] = pipr;
 
     if (pipr < sig_regs[TM_CPPR]) {

hw/intc/xive2.c

@@ -1089,6 +1089,7 @@ static void xive2_tctx_process_pending(XiveTCTX *tctx, uint8_t sig_ring)
     int rc;
 
     g_assert(sig_ring == TM_QW3_HV_PHYS || sig_ring == TM_QW1_OS);
+    g_assert(!xive_nsr_indicates_group_exception(sig_ring, sig_regs[TM_NSR]));
 
     /*
      * Recompute the PIPR based on local pending interrupts. It will