kvm: x86: Save/restore exception_index

As KVM now makes use of exception_index to keep pending exceptions, we
have to save&restore this field as well.

NOTE: We have to nail the arch-independent exception_index down to a
certain bit width for proper vmstate processing, namely to 32 bit.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit 4d6e3ac5)

cpu-defs.h

@@ -179,7 +179,7 @@ typedef struct CPUWatchpoint {
                                                                         \
     /* Core interrupt code */                                           \
     jmp_buf jmp_env;                                                    \
-    int exception_index;                                                \
+    int32_t exception_index;                                            \
                                                                         \
     CPUState *next_cpu; /* next CPU sharing TB cache */                 \
     int cpu_index; /* CPU index (informative) */                        \

target-i386/machine.c

@@ -453,6 +453,7 @@ static const VMStateDescription vmstate_cpu = {
         VMSTATE_UINT8_V(nmi_pending, CPUState, 11),
         VMSTATE_UINT8_V(has_error_code, CPUState, 11),
         VMSTATE_UINT32_V(sipi_vector, CPUState, 11),
+        VMSTATE_INT32_V(exception_index, CPUState, 11),
         /* MCE */
         VMSTATE_UINT64_V(mcg_cap, CPUState, 10),
         VMSTATE_UINT64_V(mcg_status, CPUState, 10),