Re: [Qemu-devel] [PATCH v3 2/7] hpet: Save/restore cached RTC IRQ level

[Anthony Liguori <aliguori@us.ibm.com>]

On 01/31/2012 11:41 AM, Jan Kiszka wrote:
> In legacy mode, the HPET suppresses the RTC interrupt delivery via IRQ
> 8 but keeps track of the RTC output level and applies it when legacy
> mode is turned off again. This value has to be preserved across save/
> restore as it cannot be reconstructed otherwise.
>
> Signed-off-by: Jan Kiszka<jan.kiszka@siemens.com>
> ---
>   hw/hpet.c |   26 ++++++++++++++++++++++++++
>   1 files changed, 26 insertions(+), 0 deletions(-)
>
> diff --git a/hw/hpet.c b/hw/hpet.c
> index aba9ea9..39b291f 100644
> --- a/hw/hpet.c
> +++ b/hw/hpet.c
> @@ -240,6 +240,24 @@ static int hpet_post_load(void *opaque, int version_id)
>       return 0;
>   }
>
> +static bool hpet_rtc_irq_level_needed(void *opaque)
> +{
> +    HPETState *s = opaque;
> +
> +    return s->rtc_irq_level != 0;
> +}
> +
> +static const VMStateDescription vmstate_hpet_rtc_irq_level = {
> +    .name = "hpet/rtc_irq_level",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .minimum_version_id_old = 1,
> +    .fields      = (VMStateField[]) {
> +        VMSTATE_UINT8(rtc_irq_level, HPETState),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +

This won't work.  We don't clear rtc_irq_level on reset so rtc_irq_level may be 
high or low after reset.  As such, we can't use a subsection here.  We need to 
bump the savevm state.

Regards,

Anthony Liguori

>   static const VMStateDescription vmstate_hpet_timer = {
>       .name = "hpet_timer",
>       .version_id = 1,
> @@ -273,6 +291,14 @@ static const VMStateDescription vmstate_hpet = {
>           VMSTATE_STRUCT_VARRAY_UINT8(timer, HPETState, num_timers, 0,
>                                       vmstate_hpet_timer, HPETTimer),
>           VMSTATE_END_OF_LIST()
> +    },
> +    .subsections = (VMStateSubsection[]) {
> +        {
> +            .vmsd =&vmstate_hpet_rtc_irq_level,
> +            .needed = hpet_rtc_irq_level_needed,
> +        }, {
> +            /* empty */
> +        }
>       }
>   };
>