Re: [Qemu-devel] [PATCH 7/7] RTC: Allow to migrate from old QEMU

[Michael Roth <mdroth@linux.vnet.ibm.com>]

On Fri, Jul 20, 2012 at 12:53:53PM +0200, Paolo Bonzini wrote:
> From: "Zhang, Yang Z" <yang.z.zhang@intel.com>
> 
> The new logic is compatible with old, and it should not block migration
> from old QEMU.  However, the new version cannot migrate to the old one.

Do we not plan to support 1.2 -> 1.1 with -M pc-1.1? I'm not sure what
the "official" stance is, but I think we could do it by making the behavior
configurable and defaulting to the old behavior for -M pc-1.1, and using
VMSTATE_*_TEST(..., rtc_on_demand_enabled) to send the new fields
conditionally.

> 
> Cc: Juan Quintela <quintela@redhat.com>
> Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  hw/mc146818rtc.c |   42 +++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 39 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
> index f0b75cb..d3871d8 100644
> --- a/hw/mc146818rtc.c
> +++ b/hw/mc146818rtc.c
> @@ -697,11 +697,47 @@ static int rtc_post_load(void *opaque, int version_id)
>      return 0;
>  }
> 
> +static int rtc_load_old(QEMUFile *f, void *opaque, int version_id)
> +{
> +    RTCState *s = opaque;
> +    uint8_t buf[77];
> +
> +    if (version_id > 2) {
> +        return -EINVAL;
> +    }
> +
> +    qemu_get_buffer(f, s->cmos_data, sizeof(s->cmos_data));
> +    qemu_get_8s(f, &s->cmos_index);
> +
> +    /* Skip loading of s->current_tm, we already have the
> +     * information in cmos_data.
> +     */
> +    qemu_get_buffer(f, buf, 7*4);
> +
> +    qemu_get_timer(f, s->periodic_timer);
> +    s->next_periodic_time = qemu_get_be64(f);
> +
> +    /* Skip loading of next_second_time, second_timer, second_timer2.  */
> +    qemu_get_buffer(f, buf, 3*8);
> +
> +    rtc_set_time(s);
> +    s->offset = 0;
> +    check_update_timer(s);
> +
> +    if (version_id >= 2) {
> +        s->irq_coalesced = qemu_get_be32(f);
> +        s->period = qemu_get_be32(f);
> +    }
> +
> +    return rtc_post_load(opaque, version_id);
> +}
> +
>  static const VMStateDescription vmstate_rtc = {
>      .name = "mc146818rtc",
> -    .version_id = 2,
> -    .minimum_version_id = 1,
> +    .version_id = 3,
> +    .minimum_version_id = 3,
>      .minimum_version_id_old = 1,
> +    .load_state_old = rtc_load_old,
>      .post_load = rtc_post_load,
>      .fields      = (VMStateField []) {
>          VMSTATE_BUFFER(cmos_data, RTCState),
> @@ -837,7 +873,7 @@ static int rtc_initfn(ISADevice *dev)
>      memory_region_init_io(&s->io, &cmos_ops, s, "rtc", 2);
>      isa_register_ioport(dev, &s->io, base);
> 
> -    qdev_set_legacy_instance_id(&dev->qdev, base, 2);
> +    qdev_set_legacy_instance_id(&dev->qdev, base, 3);
>      qemu_register_reset(rtc_reset, s);
> 
>      object_property_add(OBJECT(s), "date", "struct tm",
> -- 
> 1.7.10.2
> 
>