ppc/xive2: Fix treatment of PIPR in CPPR update

According to the XIVE spec, updating the CPPR should also update the
PIPR. The final value of the PIPR depends on other factors, but it
should never be set to a value that is above the CPPR.

Also added support for redistributing an active group interrupt when it
is precluded as a result of changing the CPPR value.

Signed-off-by: Glenn Miles <milesg@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Michael Kowal <kowal@linux.ibm.com>
Reviewed-by: Caleb Schlossin <calebs@linux.ibm.com>
Tested-by: Gautam Menghani <gautam@linux.ibm.com>
Link: https://lore.kernel.org/qemu-devel/20250512031100.439842-11-npiggin@gmail.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

diff --git a/hw/intc/xive2.c b/hw/intc/xive2.c
index 36e842f041e5ae038f401c66e16a0d7081281af9..c23933f8f550500fae06768c0d3085b6e598d9b9 100644 (file)
--- a/hw/intc/xive2.c
+++ b/hw/intc/xive2.c
@@ -995,7 +995,9 @@ static void xive2_tctx_set_cppr(XiveTCTX *tctx, uint8_t ring, uint8_t cppr)
             }
         }
     }
-    regs[TM_PIPR] = pipr_min;
+
+    /* PIPR should not be set to a value greater than CPPR */
+    regs[TM_PIPR] = (pipr_min > cppr) ? cppr : pipr_min;
 
     rc = xive2_tctx_get_nvp_indexes(tctx, ring_min, &nvp_blk, &nvp_idx);
     if (rc) {