Re: [Qemu-devel] [PATCH 10/12] piix: do not raise irq while loading vmstate

[Paolo Bonzini <pbonzini@redhat.com>]

Il 26/08/2014 09:15, Pavel Dovgalyuk ha scritto:
> This patch disables raising an irq while loading the state of PCI bridge.
> 
> Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
> ---
>  hw/pci-host/piix.c |   22 ++++++++++++++++++++--
>  1 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
> index e0e0946..86d6d20 100644
> --- a/hw/pci-host/piix.c
> +++ b/hw/pci-host/piix.c
> @@ -409,7 +409,7 @@ static void piix3_set_irq_pic(PIIX3State *piix3, int pic_irq)
>                       (pic_irq * PIIX_NUM_PIRQS))));
>  }
>  
> -static void piix3_set_irq_level(PIIX3State *piix3, int pirq, int level)
> +static void piix3_set_irq_level_internal(PIIX3State *piix3, int pirq, int level)
>  {
>      int pic_irq;
>      uint64_t mask;
> @@ -422,6 +422,18 @@ static void piix3_set_irq_level(PIIX3State *piix3, int pirq, int level)
>      mask = 1ULL << ((pic_irq * PIIX_NUM_PIRQS) + pirq);
>      piix3->pic_levels &= ~mask;
>      piix3->pic_levels |= mask * !!level;
> +}
> +
> +static void piix3_set_irq_level(PIIX3State *piix3, int pirq, int level)
> +{
> +    int pic_irq;
> +
> +    pic_irq = piix3->dev.config[PIIX_PIRQC + pirq];
> +    if (pic_irq >= PIIX_NUM_PIC_IRQS) {
> +        return;
> +    }
> +
> +    piix3_set_irq_level_internal(piix3, pirq, level);
>  
>      piix3_set_irq_pic(piix3, pic_irq);
>  }
> @@ -527,7 +539,13 @@ static void piix3_reset(void *opaque)
>  static int piix3_post_load(void *opaque, int version_id)
>  {
>      PIIX3State *piix3 = opaque;
> -    piix3_update_irq_levels(piix3);
> +    int pirq;
> +
> +    piix3->pic_levels = 0;
> +    for (pirq = 0; pirq < PIIX_NUM_PIRQS; pirq++) {
> +        piix3_set_irq_level_internal(piix3, pirq,
> +                            pci_bus_get_irq_level(piix3->dev.bus, pirq));
> +    }
>      return 0;
>  }
>  
> 
> 
> 

The commit message or (probably better) a comment in the code should
explain why the PIC state must not be updated, that is which side effect
is undesirable.

This would clarify whether the change is useful for migration too, or
just cosmetic outside record/replay.  Unlike other patches, however, I
think this could be acceptable even without record/replay
infrastructure, because it is not going against "accepted" patterns for
migration.

Paolo