On 30/10/16 22:12, David Gibson wrote:
> When vmstate for the ppc cpu was introduced in a90db158 "target-ppc:
> Convert ppc cpu savevm to VMStateDescription", several "sanity check"
> fields were included, verifying that certain cpu parameters matched between
> source and destination.
>
> This turns out not to have been a good idea. For one thing it's redundant
> with existing checks for a compatible cpu version at either end. But more
> importantly the insns_flags and insns_flags2 checks actively break things:
> they expose what's essentially an internal TCG implementation detail in the
> migration stream. That means that when new instruction classes are added
> or rearranged, migration can break.
>
> This removes these ill-considered sanity checks.
>
> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> ---
> target-ppc/machine.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/target-ppc/machine.c b/target-ppc/machine.c
> index 62b9e94..453ef0a 100644
> --- a/target-ppc/machine.c
> +++ b/target-ppc/machine.c
> @@ -602,10 +602,10 @@ const VMStateDescription vmstate_ppc_cpu = {
> /* FIXME: access_type? */
>
> /* Sanity checking */
> - VMSTATE_UINTTL_EQUAL(env.msr_mask, PowerPCCPU),
> - VMSTATE_UINT64_EQUAL(env.insns_flags, PowerPCCPU),
> - VMSTATE_UINT64_EQUAL(env.insns_flags2, PowerPCCPU),
> - VMSTATE_UINT32_EQUAL(env.nb_BATs, PowerPCCPU),
> + VMSTATE_UNUSED(sizeof(target_ulong) /* msr_mask */
> + + sizeof(uint64_t) /* insns_flags */
> + + sizeof(uint64_t) /* insns_flags2 */
> + + sizeof(uint32_t)), /* nb_BATs */
This breaks migration to older QEMU:
25055@1478238734.537761:vmstate_load_field_error field "env.msr_mask" load
failed, ret = -22
> VMSTATE_END_OF_LIST()
> },
> .subsections = (const VMStateDescription*[]) {
>
--
Alexey
