spapr/xive: Add a 'hv-prio' property to represent the KVM escalation priority

On POWER9, the KVM XIVE device uses priority 7 for the escalation
interrupts. On POWER10, the host can use a reduced set of priorities
and KVM will configure the escalation priority to a lower number. In
any case, the guest is allowed to use priorities in a single range :

    [ 0 .. (maxprio - 1) ].

Introduce a 'hv-prio' property to represent the escalation priority
number and use it to compute the "ibm,plat-res-int-priorities"
property defining the priority ranges reserved by the hypervisor.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20200819130843.2230799-2-clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

2 files changed, 16 insertions, 19 deletions

diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
index 4bd0d606ba..1fa09f287a 100644
--- a/hw/intc/spapr_xive.c
+++ b/hw/intc/spapr_xive.c
@@ -595,6 +595,7 @@ static Property spapr_xive_properties[] = {
     DEFINE_PROP_UINT32("nr-ends", SpaprXive, nr_ends, 0),
     DEFINE_PROP_UINT64("vc-base", SpaprXive, vc_base, SPAPR_XIVE_VC_BASE),
     DEFINE_PROP_UINT64("tm-base", SpaprXive, tm_base, SPAPR_XIVE_TM_BASE),
+    DEFINE_PROP_UINT8("hv-prio", SpaprXive, hv_prio, 7),
     DEFINE_PROP_END_OF_LIST(),
 };
 
@@ -692,12 +693,13 @@ static void spapr_xive_dt(SpaprInterruptController *intc, uint32_t nr_servers,
         cpu_to_be32(16), /* 64K */
     };
     /*
-     * The following array is in sync with the reserved priorities
-     * defined by the 'spapr_xive_priority_is_reserved' routine.
+     * QEMU/KVM only needs to define a single range to reserve the
+     * escalation priority. A priority bitmask would have been more
+     * appropriate.
      */
     uint32_t plat_res_int_priorities[] = {
-        cpu_to_be32(7),    /* start */
-        cpu_to_be32(0xf8), /* count */
+        cpu_to_be32(xive->hv_prio),    /* start */
+        cpu_to_be32(0xff - xive->hv_prio), /* count */
     };
 
     /* Thread Interrupt Management Area : User (ring 3) and OS (ring 2) */
@@ -844,19 +846,12 @@ type_init(spapr_xive_register_types)
  */
 
 /*
- * Linux hosts under OPAL reserve priority 7 for their own escalation
- * interrupts (DD2.X POWER9). So we only allow the guest to use
- * priorities [0..6].
+ * On POWER9, the KVM XIVE device uses priority 7 for the escalation
+ * interrupts. So we only allow the guest to use priorities [0..6].
  */
-static bool spapr_xive_priority_is_reserved(uint8_t priority)
+static bool spapr_xive_priority_is_reserved(SpaprXive *xive, uint8_t priority)
 {
-    switch (priority) {
-    case 0 ... 6:
-        return false;
-    case 7: /* OPAL escalation queue */
-    default:
-        return true;
-    }
+    return priority >= xive->hv_prio;
 }
 
 /*
@@ -1053,7 +1048,7 @@ static target_ulong h_int_set_source_config(PowerPCCPU *cpu,
         new_eas.w = eas.w & cpu_to_be64(~EAS_MASKED);
     }
 
-    if (spapr_xive_priority_is_reserved(priority)) {
+    if (spapr_xive_priority_is_reserved(xive, priority)) {
         qemu_log_mask(LOG_GUEST_ERROR, "XIVE: priority " TARGET_FMT_ld
                       " is reserved\n", priority);
         return H_P4;
@@ -1212,7 +1207,7 @@ static target_ulong h_int_get_queue_info(PowerPCCPU *cpu,
      * This is not needed when running the emulation under QEMU
      */
 
-    if (spapr_xive_priority_is_reserved(priority)) {
+    if (spapr_xive_priority_is_reserved(xive, priority)) {
         qemu_log_mask(LOG_GUEST_ERROR, "XIVE: priority " TARGET_FMT_ld
                       " is reserved\n", priority);
         return H_P3;
@@ -1299,7 +1294,7 @@ static target_ulong h_int_set_queue_config(PowerPCCPU *cpu,
      * This is not needed when running the emulation under QEMU
      */
 
-    if (spapr_xive_priority_is_reserved(priority)) {
+    if (spapr_xive_priority_is_reserved(xive, priority)) {
         qemu_log_mask(LOG_GUEST_ERROR, "XIVE: priority " TARGET_FMT_ld
                       " is reserved\n", priority);
         return H_P3;
@@ -1466,7 +1461,7 @@ static target_ulong h_int_get_queue_config(PowerPCCPU *cpu,
      * This is not needed when running the emulation under QEMU
      */
 
-    if (spapr_xive_priority_is_reserved(priority)) {
+    if (spapr_xive_priority_is_reserved(xive, priority)) {
         qemu_log_mask(LOG_GUEST_ERROR, "XIVE: priority " TARGET_FMT_ld
                       " is reserved\n", priority);
         return H_P3;
diff --git a/include/hw/ppc/spapr_xive.h b/include/hw/ppc/spapr_xive.h
index a1c8540ab4..26c8d90d71 100644
--- a/include/hw/ppc/spapr_xive.h
+++ b/include/hw/ppc/spapr_xive.h
@@ -49,6 +49,8 @@ typedef struct SpaprXive {
     void          *tm_mmap;
     MemoryRegion  tm_mmio_kvm;
     VMChangeStateEntry *change;
+
+    uint8_t       hv_prio;
 } SpaprXive;
 
 typedef struct SpaprXiveClass {