[Qemu-devel] [PATCH] pseries: Fix compat_pvr on reset

[Laurent Vivier <lvivier@redhat.com>]

If we a migrate P8 machine to a P9 machine, the migration fails on
destination with:

  error while loading state for instance 0x1 of device 'cpu'
  load of migration failed: Operation not permitted

This is caused because the compat_pvr field is only present for the first
CPU.
Originally, spapr_machine_reset() calls ppc_set_compat() to set the value
max_compat_pvr for the first cpu and this was propagated to all CPUs by
spapr_cpu_reset().  Now, as spapr_cpu_reset() is called before that, the
value is not propagated to all CPUs and the migration fails.

To fix that, propagate the new value to all CPUs in spapr_machine_reset().

Fixes: 25c9780d38d4 ("spapr: Reset CAS & IRQ subsystem after devices")
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 hw/ppc/spapr.c          | 8 +++++++-
 hw/ppc/spapr_cpu_core.c | 2 ++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index baedadf20b8c..d063312a3b2a 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1752,7 +1752,13 @@ static void spapr_machine_reset(MachineState *machine)
         spapr_ovec_cleanup(spapr->ov5_cas);
         spapr->ov5_cas = spapr_ovec_new();
 
-        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);
+        /*
+         * reset compat_pvr for all CPUs
+         * as qemu_devices_reset() is called before this,
+         * it can't be propagated by spapr_cpu_reset()
+         * from the first CPU to all the others
+         */
+        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
     }
 
     /*
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index bf47fbdf6f7f..45e2f2747ffc 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -43,6 +43,8 @@ static void spapr_cpu_reset(void *opaque)
 
     /* Set compatibility mode to match the boot CPU, which was either set
      * by the machine reset code or by CAS. This should never fail.
+     * At startup the value is already set for all the CPUs
+     * but we need this when we hotplug a new CPU
      */
     ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &error_abort);
 
-- 
2.21.0