pseries: fix TCG migration

Migration of pseries is broken with TCG because
QEMU tries to restore KVM MMU state unconditionally.

The result is a SIGSEGV in kvm_vm_ioctl():

  #0  kvm_vm_ioctl (s=0x0, type=-2146390353)
      at qemu/accel/kvm/kvm-all.c:2032
  camthesaxman#1  0x00000001003e3e2c in kvmppc_configure_v3_mmu (cpu=<optimized out>,
      radix=<optimized out>, gtse=<optimized out>, proc_tbl=<optimized out>)
      at qemu/target/ppc/kvm.c:396
  irixxxx#2  0x00000001002f8b88 in spapr_post_load (opaque=0x1019103c0,
      version_id=<optimized out>) at qemu/hw/ppc/spapr.c:1578
  irixxxx#3  0x000000010059e4cc in vmstate_load_state (f=0x106230000,
      vmsd=0x1009479e0 <vmstate_spapr>, opaque=0x1019103c0,
      version_id=<optimized out>) at qemu/migration/vmstate.c:165
  qemu#4  0x00000001005987e0 in vmstate_load (f=<optimized out>, se=<optimized out>)
      at qemu/migration/savevm.c:748

This patch fixes the problem by not calling the KVM function with the
TCG mode.

Fixes: d39c90f ("spapr: Fix migration of Radix guests")
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Author: vivier

hw/ppc/spapr.c

@@ -1570,7 +1570,7 @@ static int spapr_post_load(void *opaque, int version_id)
         err = spapr_rtc_import_offset(&spapr->rtc, spapr->rtc_offset);
     }
 
-    if (spapr->patb_entry) {
+    if (kvm_enabled() && spapr->patb_entry) {
         PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
         bool radix = !!(spapr->patb_entry & PATBE1_GR);
         bool gtse = !!(cpu->env.spr[SPR_LPCR] & LPCR_GTSE);