[RFC PATCH 3/4] hw/ppc: Take nested guest into account when saving timebase

[Fabiano Rosas]

When saving the guest "timebase" we look to the first_cpu for its
tb_offset. If that CPU happens to be running a nested guest at this
time, the tb_offset will have the nested guest value.

This was caught by code inspection.

Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
---
 hw/ppc/ppc.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index 9e99625ea9..093cd87014 100644
--- a/hw/ppc/ppc.c
+++ b/hw/ppc/ppc.c
@@ -36,6 +36,7 @@
 #include "kvm_ppc.h"
 #include "migration/vmstate.h"
 #include "trace.h"
+#include "hw/ppc/spapr_cpu_core.h"
 
 static void cpu_ppc_tb_stop (CPUPPCState *env);
 static void cpu_ppc_tb_start (CPUPPCState *env);
@@ -961,19 +962,33 @@ static void timebase_save(PPCTimebase *tb)
 {
     uint64_t ticks = cpu_get_host_ticks();
     PowerPCCPU *first_ppc_cpu = POWERPC_CPU(first_cpu);
+    int64_t tb_offset;
 
     if (!first_ppc_cpu->env.tb_env) {
         error_report("No timebase object");
         return;
     }
 
+    tb_offset = first_ppc_cpu->env.tb_env->tb_offset;
+
+    if (first_ppc_cpu->vhyp && vhyp_cpu_in_nested(first_ppc_cpu)) {
+        SpaprCpuState *spapr_cpu = spapr_cpu_state(first_ppc_cpu);
+
+        /*
+         * If the first_cpu happens to be running a nested guest at
+         * this time, tb_env->tb_offset will contain the nested guest
+         * offset.
+         */
+        tb_offset -= spapr_cpu->nested_tb_offset;
+    }
+
     /* not used anymore, we keep it for compatibility */
     tb->time_of_the_day_ns = qemu_clock_get_ns(QEMU_CLOCK_HOST);
     /*
      * tb_offset is only expected to be changed by QEMU so
      * there is no need to update it from KVM here
      */
-    tb->guest_timebase = ticks + first_ppc_cpu->env.tb_env->tb_offset;
+    tb->guest_timebase = ticks + tb_offset;
 
     tb->runstate_paused =
         runstate_check(RUN_STATE_PAUSED) || runstate_check(RUN_STATE_SAVE_VM);
-- 
2.34.1